While the scroll bar is active when there are enough actions undertaken to require it, it also is active sometimes when very few actions have been undertaken, such that the scroll, while present, is entirely unnecessary. This leads to the scroll appearing, then disappearing, only to reappear later. I assume this is unintentional. It's not a major issue by any means, but fixing it would be nice, if the time is available.

It should be fixed now, thanks for reporting.