Hi there, first time posting this is an issue myself and a colleague have found when copying a 4x5 sequence (1080x1350), then changing the new sequence settings of the copied sequence to 9x16 (1080x1920).
It's an issue I believe related to auto reframe where it will disable motion, which I'm aware it's supposed to do. However, the issue I'm encountering is it is auto-switching between the two modes; auto reframe and motion, which is leading to errors in frame size in exports, as the motion settings seem to be disabling on random clips.
I was encountering this on the previous update to version 15.1.0 (build 48) and still encountering it on the latest update.
In the previous update, I stopped using the auto-reframe sequence I thought that might be the issue, but it seems to be happening when auto-reframe effect is added manually too.