https://bugs.winehq.org/show_bug.cgi?id=43737
--- Comment #13 from Zebediah Figura z.figura12@gmail.com --- Created attachment 67532 --> https://bugs.winehq.org/attachment.cgi?id=67532 hack out erasing the parent in USER_SetWindowPos()
The attached patch fixes it for me.
It hangs because the parent stops processing messages. Hence 5c8903a0a9 probably made it better, but unlike bug 48732, for one reason or another destroying the child exposes the parent, which synchronously sends a WM_ERASEBKGND message, causing a hang.