Kiruna

Well, I figured out what it was. Corrupt models for fbi and police4 from a pack I downloaded a month ago. Not sure how that happened, but it's peachy now. Isolated it purely to emergency vehicles (because that's all I've modified), and figured that maybe LSPDFR might be checking the core set of vehicles when you go on duty. Maybe so that it can add them to the police garage? Regardless, I found the problem models with that in mind. It was also made easier by seeing that OpenIV crashed when I tried to open the corrupted model. Thanks for the help, at least for the rubber ducky assistance. ✌️ OP, it might be worth going through and looking at the models for every police vehicle you have(or have modified) in OpenIV's model viewer, or just spawning each one of them in game. If the game crashes when you spawn a specific vehicle, it's probably good to look closer at it, and try replacing it. Since it's happening when you go on duty, I wouldn't be surprised if it's one of the core 'Emergency' vehicle models. This is anecdotal, but hope it helps.

No dice there. I gave this a shot even though my host file is relatively empty, outside of some local entries. I did try renaming my mods folder and it looks like I'm able to go on duty without issue; it's something within my modded update.rpf or dlc.rpf files that might be causing the issue, even after reverting to backups I made before adding the aforementioned vehicle mod. The solution for me is kind of obvious, start over and install mods and addons one-by-one, but let me know if there's a way I can go about narrowing down what might be causing this. Not to take away from Fhsig13's original post - but maybe my experience might help here.

Bump - I'm having this exact issue, same use-case that causes it too. Only when I go on-duty. Mods are all in my Mods folder, and while I initially received this after installing some addon vehicles, this issue now persists even after reverting everything to backups.