i did a search on this thread and someone mentioned it but there was no solution on how to fix it.
i believe the widgets are still opening, except that they remember the last location which is outside of the screen and therefore will open at that location, which is outside of the screen.
it happens in PIE as well and when you build the game.
i have not tested but since changing the resolution makes the screen “bigger”, i guess it would explain the problem but doesn’t fix it, since in the first place, the widget shouldn’t be allowed to fly off the screen and changing into a bigger resolution every time this happens isn’t a fix…