Scroll bar on Project Settings - Collision menu behaves strangely.

The scroll bar in the Engine - Collision menu in Project Settings doesn't appear when it first should, and when it does, it resizes and moves oddly.

Edit MattK: variable length widgets inside of a virtualized scrollbox exhibit this behavior

1. Open Project Settings.
2. Select Collision from the left panel.
3. Expand the Preset category. Notice that the information goes off the bottom of the panel, but the scroll bar appears for only (what looks like) one frame before vanishing.
4. Collapse and re-expand the Preset category. Notice that the scroll bar appears this time.
5. Scroll the bar up and down. Notice that the bar changes size and position in an unexpected way.

See attached video.