Right hand edge in Galley view covered in Dorico 4

[dspreadbury]

Please see this thread:

First few notes in D4 and some unexplainably weird behaviour

Thank for your hard work! But some weird behaviour just occurred. I‘ve just typed some notes into an old D3.5 file and immediately got stuck. When I type in notes in galley view and the notes reach the right edge of the screen galley view doesn‘t move on at all. I even can‘t move the scroll bar any further to the right. Why is this happening? Thanks for your help and a very happy new year to you all!