I would need to move the symbol for the end of proof - a square a little bit up but ONLY on one slide, where the proof is quite long and the square has not seen very much.
It's difficult to provide precise advise without a minimal working example; however, the following code reproduces the problem mentioned:
the output shows that the qed symbol for the last
Adding a convenient
One has to be careful about the length used for the
As a personal note, you should reconsider using frames containing too much text (sometimes it's unavoidable, but give it a second thought).