cherryaerie

Usually, it is a trainer that does something like that, what modification did you install by chance? If it was something in the mods folder, you can delete the modified files in the mods folder and copy it from outside the mods folder, and paste it to the mods folder.

First things first, ensure that there are no conflicting texture/model files. Model files (.yft) should only have another model file corresponding with that vehicle. (Ex; If you have a Tahoe in that spot previously, and your new Explorer does not replace the previous Tahoe files completely.) Easiest way to check this is to simply delete all your modded replace sheriff2 files and then reinstall them to ensure there are no conflicting files. Also ensure you have no addon vehicle files that have the same name.

You can go to the same pathway you had the cars and copy+paste them into the mods folder, or you can simply delete your new modded files and the files outside the mods folder will work just fine, you just cannot modify those files.
 
Usually, the result of your images is the result of models and/or texture files conflicting and not belonging to the model. Green/Black&White Checkers typically indicate missing textures.

I'm not sure whether you mean LSPDFR or GTAV itself. If it is GTAV itself, go ahead and update your normal install version. For LSPDFR, keep it on the current version until an update comes out for LSPDFR and RPH, and ScriptHookV if you prefer. From there you can simply copy GTAV, PlayGTAV, GTAVLanguageSelect, and GTAVLauncher from your updated folder to the LSPDFR folder when you do wish to update everything.
 
To start that, turn off automatic steam updates, manually update your normal version, and then turn off your automatic updates. I strongly encourage that you backup your old LSPDFR game version with the 4 files stated above in case Steam decides to update that version, but it should only do it once.

If your game does not work, its likely because of that file. I recommend uninstalling that and trying to run the game again. If it works, it is that file, if not, it is something else in your mods folder.

No, you're fine, between dealing with 2 of my own kids and typing this out, it just takes some time to type out.
 
I have also forgotten to mention that you will need to enable tools for ASI plugins. In OpenIV, go to the "tools" tab and open "ASI Manager". Click install on all 3 and click save. 
 
For Resource Adjuster, all files (except the read me) will go into the main game directory. Siren Setting Limit Adjuster is not required and will not function unless you have a car that needs this, but will be installed to the main game directory.
 
For Thero's State Wide Services Pack, as all addon packs, follow;
 
 
As Los Santos Protection Squad is a really old plugin so I cannot guarantee it will work unfortunately, but it it has a readme inside it. Just open the main game directory and drag and drop the "lspdfr" and "plugins" folder from the download into the directory. If it asks you to replace anything, you can safely replace it.
 
As for your vest textures, there are a few that match this title. Unfortunately, I am not familiar with the pathway for male characters to replace a single texture, and the one I found doesn't provide information beyond the texture name. If anyone happens to read this and knows, feel free to let him know as I cannot answer that confidently. 
 
To install EUP and EUP Packs;

LSPD First Response: Exception type: System.Xml.XmlException
LSPD First Response: Exception message: Data at the root level is invalid. Line 28, position 1.
 
You have recently modified the file stations_sahp.xml from lspdfr/data/custom/ that cannot be parsed. There is likely an extra space or other character at the start of line 28 that is not meant to be there.

When launching RPH, hold your left shift key in for about 10 seconds to bring up the settings menu. Change your plugin threshold timeout value to 60000 and try again.

I don't know what the reason that it suddenly started occurring for, but you can workaround it to get back to playing LSPDFR (I am not quite sure how to fix it to straight launch from desktop otherwise unfortunately).
 
Launch Steam and Launch GTA. Make sure that you select play story mode and NOT online.  Get past the loading screen (police chase, shootout, and any custom loading screens) When you get the option to select story mode, online, and whatever else, alt+tab. Launch RPH from your desktop. You may need to click it twice if it does not initially open. Wait for it to disappear to the bottom left of your screen. Click play story and it should start loading your plugins.

I figured this out this morning the hard way and only figured this out because I had been talking to the developer of the mod as I was doing it, so "credit" for this answer goes to him, I am just sharing it.
 
SimpleCTRL checks for your seatbelt to be enabled/disabled in the game, so when a mod like Faya's Seatbelt or Simple Trainer "enables" your seatbelt, it doesn't allow you to leave the vehicle (as intended), so please for the love of sanity, do not go to the mods download section and claim its a bug. 
 
Anyways, if you have a trainer, ensure your vehicle's god mode is disabled, and your seatbelt is disabled through the trainer and any mod. You may need to enable and disable the seatbelt option in your trainer.  

If they are addons, you likely installed them as a separate DLC and not in the latest patch day. Addon vehicles will not replace the default units. There are a few things you can do to change that, but the easiest thing to do would be to take the vehicles from the addon and rename each of them to replace a vehicle slot so they respond instead of the default units.
 
Your other option would to be go into every data folder and change police models there to the names of your addon vehicles.

Download/Reinstall RageNativeUI to the main game directory.

Remove OP Immersive Dispatch.

Install CalloutInterfaceAPI from either the callout interface download or from whatever callout pack you recently installed.

There is an issue with your FBI2 model (hash 0x9dc66994) that the game cannot load. This may be the model itself, or a meta file. I would revert any changes you made to its entries from meta files, and ensure you have the vehicle installed properly.

With the newest update, a lot of people seemed to have issues with their mods folder. Since renaming your mods folder allowed the game to launch, give the following steps a try.
In mods/update, delete update2.rpf and try loading the game. If this works, there is no need to proceed to the next step.  Open the main directory and locate the update folder. Open this and copy the update.rpf located inside (not the 2nd one if it is there).  Visit mods/update again and paste that copied update.rpf into that folder and try loading the game again.

The vehicle is missing a flag. Find the vehicles.meta within the addon and find the slot. Find the <flags> argument and add the following;
 
FLAG_LAW_ENFORCEMENT FLAG_EMERGENCY_SERVICE
 

You can do one of two things. Either replace the gauntlet with another vehicle, for example, a hellcat, or remove/replace the entry with the update.
 
For replacing the car, rename the car files you want to replace to polgauntlet and place it in the same location you install the rest of your police vehicles. Do not remove tags such as _hi or +hi as that can mess with the model and texture files of the car.
 
If you just want to remove it as its entirety without seeing it as a different vehicle as I mentioned above, follow the below instructions;
Go to the path Grand Theft Auto V\lspdfr\data and locate agency.xml Open via a notepad or XML code reader. If you need it, I would recommend Kate XML Editor. (I personally use this) Search for "polgauntlet" via CTRL+F  Either replace this with another vehicle slot (Ex: police2, sheriff2) or remove the entirety of the entry line. Line will look something like this: <Vehicle is_dlc="true" use_modkit_liveries="true" livery_multi="4,16,19">polgauntlet</Vehicle>  
Since this forum became a little more popular than I really anticipated, those who come here in the future looking to remove the new Police Crown Victora released with the chop shop DLC, the same method applies, except it is named "police5", so search for that instead.

Install IPT.common/reinstall Callout Interface.

Ok, please try the following:
Open your main directory and open the update folder. Copy the update.rpf located in this folder. Go back to the main directory and locate your mods folder. Paste (control v) and select replace files. Delete update2.rpf if you have this in the mods folder.

"Unexpected XML declaration. The XML declaration must be the first node in the document, and no white space characters are allowed to appear before it. Line 2, position 3."
 
My guess is the file from lspdfr/data/duty_selection.xml. You are missing the beginning argument <xml>. If you have trouble locating it, send a screenshot and quote my message, and I will get back to you as soon as I can!

I would recommend posting in GTAV & RPH Support next time to get a faster answer for these types of issues, though someone will likely move it there when they see your post. 
 
That vehicle slot is tinted, as the fact that the sheriff2 and pranger slots are default tinted because of the corresponding base game counterparts. Find vehicles.meta in the pathway mods/update/update.rpf/common/data/level/gta5. From there, edit the file and search for the corresponding vehicle slot name, such as sheriff2, and find the "diffusetint" value. Change this value to 0x00FFFFFF.
 
In the end, that portion of the code should be <diffuseTint value="0x00FFFFFF" />

"Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system can not find the file specified"
 
Remove Section136Callouts.

Your FBI2 slot is considered invalid. You likely messed up something when installing the model. Either find a new model, or delete the FBI2 files and reinstall the model completely. 

Apparently, at the moment, Epic Games Services is experiencing an outage, which includes a majority of their services. Stay up-to-date with the outage on their status page below, and let us know if thats a continuos issue after they have resolved the outage.
 
https://status.epicgames.com/