BattleEyePolice

SOLUTION UPDATE:

Turns out that the "fix wheel turn back" (the feature where you can keep your wheels turned/locked after leaving a vehicle) or whatever it's called in the QUANTV Trainer menu had seemingly been the culprit of this issue, though I still have no idea how such a simple feature can mess the AI this much. Anyways, the moment I turned this feature off and restarted the game, I've conducted multiple traffic stops, drove around the entire map, and the issue hasn't happened since. That's probably also why it had been so inconsistent, because I actually left the wheels of my car turned only during SOME traffic stops. And after the first one, where this feature was engaged, the game just broke. It's weird, but it is what it is.