I'm having trouble with tilted horizons in my pictures and videos. I've tried calibrating the gimbal but I've still had some problems. Is there something I can change in the settings to fix it?

No. The majority of us are having the same issue. You can make a gimbal adjustment but it will go back to the tilt. I believe you can also press the C2 button and turn the dial on the right side until it's leveled. There are a few threads all about this. Do a search and you will see its a common problem.

Which Phantom do you have, and at latest build ?

I just updated my P4 yesterday (1.1.410 & DJI GO 2.8.3), prior to that I had been getting intermittent problems with horizon, seemed to happen after a yaw turn, then would level itself out after a short while.

The Juries still out but After my upgrade I did all calibrations Sensor cameras, IMU, Gimbal, RC controls & Compass. I then hovered and set my camera (using grid overlay in camera settings (the spanner)) so that it was dead level by holding the C2 button and using right wheel to set level. I flew later yesterday afternoon and grabbed about 30 minutes of video. I cannot see any example of tilted horizon in this video, so I am now hoping that this has been resolved.

Adjusting the gimbal roll is definitely something you can do. If you have not done so already, I would recommend performing an IMU calibration then a Gimbal calibration in that order to try to correct the issue before adjusting the roll manually.

Ok thank you. I have the p4 and I just updated it so I'll try adjusting tomorrow