Just open a "System settings" window, make it small (to make scrollbar to appear) and try to scroll down then move mouse pointer inside the window and scroll down again - scrolling handle jumps back. It seems that it happens when I set mouse pointer over buttons (for example, Window management or so). Reproducible: Always
I can't reproduce this. Would it be possible to make a screencast?
I can't reproduce either, although I'm not entirely sure I understand the steps. Screencast would be helpful, but please try upgrading to Plasma 5.5 and Qt 5.5 first. Then reopen this issue if you can still reproduce. Thanks