Scrollbar has fixed size and sometimes is so big that it can't be dragged.
In the screenshot you can see 4 entries but there are actually 6. The widget is however so small that dragging the scrollbar with mouse is impossible - i have to click the down arrow (or... thinking about it now... use the mouse wheel but mine is broken so it didn't occur me until now ;) ).
The underlying issue is that the scrollbar has a fixed size but increasing the side of this widget would be a nice thing too.

Happens because slider has fixed size - https://github.com/rg3dengine/rg3d/blob/master/rg3d-ui/src/scroll_bar.rs#L516
@mrDIMAS will decreasing the minimum size here help?
https://github.com/FyroxEngine/Fyrox/blob/7de5a3107da2dfab180fd23f4c79b2542b466d70/fyrox-ui/src/scroll_bar.rs#L548-L555
I think the size of the indicator should be adaptive to the actual size of the content of a ScrollViewer. This issue is a bit more complex than just decreasing the size, simply because currently the size is fixed and decreasing it would result in quite unusable scroll bar.