I usually use a pen tablet rather than a mouse, and there’s some issues:
(1) When I move the cursor across a boundary between two things it changes to a double arrow (as if you were going to move the boundary) and stays like that rather than changing back to normal. I can still click on buttons and after doing that the cursor will return to normal.
(2) Also on the timeline the cursor won’t change at the edge of a clip or highlight the boundary, although if I click in the right place I can still adjust it.
(3) On the timeline I can’t click on the scrollbar, instead it moves the playhead, as if the scrollbar wasn’t even there.
(4) On the filter list for example, I also can’t click on the scrollbar, and sometimes it starts scrolling down automatically, and other times when I hover over something it’ll highlight something a few spots down the list.
Originally I thought this might be a problem with my distribution (Ubuntu Mate 18.04 and Shotcut 19.12.16, same problem with 16.04 and 19.10.10; it’s an old Wacom Bamboo Tablet), but before I gave up I tried my mouse (which is plugged in at the same time) and everything worked fine. I don’t think I’ve had issues with any other programs (for example in GIMP you can set up the stylus/eraser separately, but they’ll work like a mouse without doing that). Display Method: OpenGL vs Software (Mesa) didn’t make a difference.
I uploaded two videos, one using the pen (bugged) and one using the mouse (correct).