Spent that past few hours trying some stuff out, i think the issue is Police Smart Radio rather than Traffic Policer.
Both out my game, i'm able to perform traffic stops, ask for ID etc, all fine. Traffic policer in on its own seems to work ok, no crashing on traffic stops. Add in smart radio, the crash asking for ID comes back.
I also have a weird ambient crash i can't quite figure out right now, a look at the logs seems to suggest something different every time but seems most consistently linked to LSPDFR spawning in police models nearby. Sometimes doing it spawning in an officer, sometimes a police car (obviously containing an officer, so i think the ped model may be the root of it)