https://bugs.winehq.org/show_bug.cgi?id=55417
--- Comment #1 from Esme Povirk madewokherd@gmail.com --- Do you have a sense of whether WM_SYNCPAINT usually happens at consistent times? From what I understand, it must have been caused by something happening in another thread. Since this particular test doesn't involve multiple threads, I assume it's caused by another process (perhaps a window being hidden).