https://bugs.winehq.org/show_bug.cgi?id=56429
--- Comment #14 from Ken Sharp imwellcushtymelike@gmail.com --- (In reply to Ken Sharp from comment #13)
(though it also occurs in a Xephyr window with Marco and "effects" off).
The opposite is true: it does NOT occur in a Xephyr window, as I said previously (oops).