so ive been dealing with this for a few weeks now and its starting to drive me crazy. im running a Gremsy T3 on a hex with a Sony A7R III and everything looks perfect on the ground, horizon is level, pitch and roll response feels tight. but somewhere around 8-12 minutes into a flight the horizon starts to drift, usually rolls left maybe half a degree, sometimes more. its gradual enough that i dont notice it in the live feed but when i pull the footage its just slightly off and ruins the shot.

ive recalibrated the IMU like three times, tried redoing the motor tuning in pixy, even remounted the whole thing thinking maybe the vibration dampers were worn out. no change. battery is a 6s 10000mah so its not a voltage sag issue as far as i can tell. anyone seen this before or is my IMU just toast

had almost the exact same thing happen with a Gremsy H16 last year. turned out to be heat ? the IMU was getting warm from the camera body radiating onto it and the gyro was drifting as the temp changed. i ended up putting a small piece of foam between the camera plate and the gimbal body and it basically fixed it. worth checking if the drift starts correlating with how hot your camera gets, especially if youre shooting in a warm environment or direct sun.

might also be worth checking your CG is actually balanced and not just close. ive read that if the payload is even slightly nose or tail heavy the motors are constantly fighting it and they can start to lose accuracy as they heat up. the T3 is pretty robust but its not magic. also what firmware are you on? there was a pixy update a while back that messed with some peoples PID settings without them realizing.