Ok, I had this issue yesterday, and I had noticed another issue with the Falcon rotator - and this time I had error logging on. They may be connected.
When I load an image to "load and slew" the rotator moves to the appropriate position - but then the system seems to not realize that. The status keeps showing "Setting position angle to..." and the solver never continues. I have attached the error log. Since the solver thinks the rotator is still moving (which it isn't), perhaps this is why the rotator won't let me choose to rotate after a flip.

I don't know. These may be two separate issues. To get the solver back, I have to disconnect the rotator after it moves.