https://bugs.winehq.org/show_bug.cgi?id=44823
--- Comment #8 from Vlad vblanton@gmail.com --- a recent steam client update may have fixed this issue inadvertently?
"Linux:... Fixed an issue where the system might become temporarily unresponsive after exiting the client due to events accruing in the window system" (https://store.steampowered.com/news/42269/)
I don't have steam installed on wine anymore, cannot test. I don't think I had this issue anymore in any case.