TXC Dagur

Couple different suggestions here:
 
For the vehicles not pulling over, try changing this setting (ElsTrafCtrlOn) in your ELS.ini to false.
 
Next, for the backup vehicles, do you have plugins such as Ultimate Backup installed? You may can mess with the .ini in that to force units to have lights and sirens on when requested.

I know this topic is years old but I wanted to comment here since I found it on Google.  For the life of me, I could not understand why random police bikes were spawning on the road from time to time.  No riders at all.  In fact I could not even ride it myself.  

It has to do with the vehicle.meta file.  In particularly it had more to do with the handlingID.  For some reason it was set to police2 instead of policeb. 

Just responding here encase you found this thread on Google.  My advise is to replace the vehicle.meta file in your mods folder with the original and see if it makes a difference.    

Fellow LSPDFR players, this might be a dumb suggestion, but why don't the creators of LSPDFR just re-release the previous build of LSPDFR that works for 2612?

just release all versions incase we need to downgrade or some crap gta 6 is gon come out in like 2 years anyway, might aswell be preparing to retire lspdfr
In all seriousness yes they should release all versions bundled up just in case some gta 4 crap happens and we need to downgrade gta 5

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here dude. Click on whoever provides gta for you. then click on the desired previous game version. assuming it would be 2612. This allows you to downgrade game versions from the recently updated 2628 to 2612. make sure your auto update is turned off. Script hook v will now work in this downgraded version.
If you need any help ask me.