On a Mac using Chrome, do the following:
# Make sure you are on a version of [[ https://en.wikipedia.beta.wmflabs.org/wiki/Special:RecentChanges | beta Recent Changes ]] with plenty of results (because vertical scrolling is required).
# Click the Active Filter Area to open the RC Page dropdown filter panel.
# Place your cursor as a user typically might, in the middle of the dropdown panel.
# Use a scroll wheel or double-finger touchpad touch to scroll the dropdown panel.
**Result:** when the scroll controls at right of the panel show that you've scrolled to the bottom of the panel, the page itself starts scrolling, BUT the cursor does not move relative to the page or the panel. It stays in the center of the panel. At some point—presumably when the page thinks the cursor has moved off the panel—the panel suddenly and jarringly closes.
**Expected result: ** The thing that makes this jarring is that, from the user's POV, the cursor is still on the panel, yet the panel suddenly closes. IMHO that is a bad bug. I'm not 100% sure what should happen: whether the page should NOT scroll when you hit the bottom of the panel (and you would just stop?), or whether the page should scroll but the cursor should move down, as it normally would when the page scrolls. Either would be fine, I think. They key is that the panel shouldn't close while the cursor is still visually hovering on it.
@Mooeypoo says this is probably related to OOUI, and that it happens only on a Mac. @Pginer-WMF, what is the desired behavior? @Volker_E, is this something in OOUI?