There have been previous visual bugs (certain UI disappearing like the context menu) and things like that, but usually the widget reflector can generally still see it while your monitors may not. In your case the widget reflector couldn’t even see the slate panel that holds it, kind of like it was removed entirely. So while it’s definitely possible and Unreal has a history of an issue like it, the hallmarks for that aren’t quite the same.
An example of driver/multimonitor setups causing shenanigans.
that said it’s not quite the same as your issue here.