I noticed that the scroll bar of the e.g. Details panel of the Editor 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 when I drag & move the scroll bar with the mouse because the moved content of the panel seems to move very inconsistent at different speeds, though I move the scroll bar at the same speed. The scroll speed seems to be consistent when I use the mouse wheel.
Thank you for submitting a bug report. I have reproduced the issue and logged it as UE-40387 which you can track on the following link: Unreal Engine Issues. Please be aware that since the issue must be reviewed and prioritized by our development staff, it may be a while before it can be addressed.