Me too. It appears to be related to the external monitor I have plugged in. Also using a bluetooth keyboard, if that matters. The cursor does not appear to move using arrow keys, but when text is typed it inserts it into a new location as if it had followed the cursor keys.
I was using it this morning in laptop mode fine.
2018 MBP, 15in. MacOS 10.14.5, Storyist 4.0 (12561)