This comes up every so often and there is no easy solution to this. In order for lists to maintain performance we destroy any element in the list that is not visible. This means that we do not know the size of the entire list and cannot determine the scroll bar size except by what is on screen. As very large elements come and go from lists the scrollbar changes size because the size of the elements on the screen changes. Ideally every list item would be uniformly sized but that is not possible in a details panel.
The user describes this issue as [the Scrollbar] "resizes when it is moved. Sometimes it even starts to flicker for one frame ( showing a very long scroll bar )."
"This looks and feels very weird ...because the moved content of the panel seems to move very inconsistent at different speeds. However, the scroll speed seems to be consistent when [moved] the mouse wheel."
Regression: No
#Open any project with Starter Content
#Select any object in the Viewport
#Size the Details panel so that it is necessary to use the Scroll bar *This may take opening a few drop down menus
#Move the Scroll bar up and down
RESULT: Scroll bar changes sizes erratically, sometimes dramatically depending on the length needed to scroll
EXPECTED: The Scroll bar to retain one size when being moved up and down
na
Head over to the existing Questions & Answers thread and let us know what's up.