I can replicate what you describe only if at step #1, the rotation lock is engaged with the iPad already in landscape. Is that what you’re doing?
If so, then I believe the behavior you describe is normal. When the app re-opens with a single camera selected and with orientation locked in landscape, it properly thinks the iPad IS in landscape (even if it’s not physically) and displays the landscape view of the camera.
What we really need is full landscape support throughout the app. There’s a Roadmap topic for that already, linked below. I’d suggest you hop over there and vote for it. Make sure to click the VOTE button at the top. Add any comments you wish at the end.