had the same problem. it was the vehiclelayouts.meta file that u change when for example downloading a bearcat (never doing that shit again lmao). touch it and it can ruin slots like sheriff2, pranger, police3. i hope i could be of assistance. if you need the file, hit me up and i will search it and copy it for you since it is nowhere on the internet to be found (i flippin spazzed when i found that out xD). That should fix it, but you can not use the bearcat properly, i recommend replacing it with the original.
best regards
hit up https://de.gta5-mods.com/vehicles/more-police-cars-to-add-v1-2 , my main man even has some videos that go into detail about how to use it.
cheers