https://bugs.winehq.org/show_bug.cgi?id=51526
--- Comment #10 from Gabriel Ivăncescu gabrielopcode@gmail.com --- (In reply to Rafał Mużyło from comment #9)
I believe I've stumbled upon something similar.
An app work fine if fullscreen, but if you switch it to windowed, its window 'disappears'. By that I mean it seems to be moved partially off screen and unmapped - this is learned via xwininfo. If wmctrl is used to activate it, it shows up, but refuses to accept mouse input (not sure about the keyboard).
Problem also happens if you get it to start windowed.
Are you sure it's only partially moved off screen and not completely? To be honest that really sounds like bug 15346. Having it unmapped when it's completely moved off screen is intended, but if it's only partial, it would be interesting to know why it happens.
What app is that? If it can't be tested, can you provide logs with +x11drv,+event,+cursor,+system,+win,+msg,+message ?