Hi everyone and thanks in advance for any help!

Twice in the last week I have had an issue with the gimbal suddenly (intermittently) not correcting during a roll, resulting in the horizon going WAY off. The first time it happened I did a cold IMU calib and gimbal calib and the problem was gone. Then only two flights after that it happened again. I landed, shut it down and restarted, and the problem was gone. Hasn't happened since in about 10 flights. Any thoughts on what could be causing this? Sorry if this a known issue and has been covered in other threads, I haven't been able to find anything about this type of sudden loss of gimbal adjustment.

I have not yet upgraded FW to the new 1.3.0 yet as I'm due to take the P3P overseas for work in 10 days. I don't like the idea of upgrading FW and discovering new problems as I've done extensive testing on the current FW and I know its devils, as opposed to the devils you don't know. Aside from this problem, at least. Ha.

Thanks again if anyone has any insight!

-Rod

Any input would be appreciated!

Sorry....I read your post, but don't have any idea what may have happened.  'feels' like something didn't initialize properly when you booted that 1 time.

My horizon also drops significantly left, after 1.3.20 'upgrade', in every flight, but quick roll levels it for a time, often enough to shoot a nice video.

what function is assigned to the buttons at the bottom side of your RC?
unintentionally pressed one of them? (the right one, top view, has had exactly this function by default at my RC)

Something just dawned on me that might be your issue.  Are you using the camera in FPV or follow mode?   Follow mode will keep the camera level at all times, FPV, however, will tilt to the left or right when you turn  (just as if you were a tiny pilot in the quadcopter and you turned, the horizon would slant in your FPV)