REGRESSION: Yes, this does not occur in 4.17.2
If the user is using any of the Content Browser menus while there's an active toast, the menu will suddenly be dismissed. It appears to get dismissed if the user attempts to use a submenu (such as Filter > Animations).
I could not reproduce this issue on Windows.
The menu is dismissed suddenly
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-50602 in the post.