Ubuntu 20.04.1 LTS What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit?
20.10.31 Can you repeat the problem? If so, what are the steps?
Load a video into the timeline that is longer than the timeline! Use a pencil of a graphic tablet and try to use the scrollbar to scroll the timeline! Experience that you can’t hit the scrollbar and instead the cursor of the play-head will be moved!
I reproduced this problem on Linux only - not macOS or Windows. It is due to using an older, deprecated GUI API. I reproduced it as well in a sample application also based on that older API. But the same sample based on the new API works. We started migrating to the new API in the most recent release 20.11, but it will take a couple of months to complete.