Masking tool not working correctly

For some reason both positive and negative masks are doing the same thing. I am not sure how exactly to explain so I brought a video

EDIT: making my display duplicate rather than extend seems to fix the issue. So i am not sure the cause


I’ve no idea what’s going on, unless you have some sort of sticky key setting on for the Alt key.

No I dont. In the vid it showed both Mask + and Mask - but they did the same thing. It is a really weird thing