I have also noticed this and yes, it seems consistent with what others have said. It's happened to me when I accidentally spread a pedestrian evenly across the tarmac, like the pedestrian was butter and my Caliburn the knife
I'll get a star and some cops will start shooting at me, but I'm already driving at speed so I'm outta' there and the star's gone fairly quickly. Then I'll be driving through that area again, perhaps days later in game-time & having travelled several km away since, and I'll suddenly get a star for seemingly no reason at all. I only noticed it because it always happened in the exact same place.
I haven't tried murdering the few cops in the area
then driving off, to attempt to reset the area. I don't bother engaging with NCPD because it's certain to be a losing battle if I fight long enough and there's no incentive in-game to fight them. Also, the lowest tier (the only ones to ever spawn like this for me) aren't much of a threat, especially if I'm inside a vehicle. I always just drive straight past them, only once did I want to stop in the area (there's a clothing shop). I found that as soon as I walked into the shop the combat state was automatically cancelled, so it didn't stop me picking up some sweet threads.
I think there are only 2 areas of NC that are affected by this in my game. It's not a big deal for me though because there's not many reasons for me to go back there. I've completed everything to do in those regions.