I'm able to reproduce the issue with this video. I'll look into it. It seems to only affect HLS streams with variable resolution. So it is likely not updating the zoom properly since the aspect ratio doesn't change, but the size does.

Opening in portrait:

Rotate to landscape:

Closing and opening again sometimes fixes the portrait view, but rotating usually jumps to a zoomed-in (and, randomly, occasionally a zoomed-out) view.