Update: It’s just spool up ratio on the gyros.
A craft which was previously stable in both vizzy aided flight and clasical gyroscopic heading lock now is unable to hold any heading at all. Perhaps this is something to do with gyroscopes or angular velocity, which regularly fluctuates when put in motion without any additional input.
@Pedro I also have a craft which, when heading lock on any heading even from a static state in orbit, will begin to apply rotation on both rcs and gyroscope. I do have some clipping designed in, but I also removed part collisions. I was going to make a post but it may be related so idk.