hi there, i'm having a similar problem where the mask gets ignored by the quad completely.
in other words, the mask is created inside the quad, but content is still visible inside the quad. restarting madmapper fixes the problem, but obviously i cannot do this mid show.
this error occurred on both madmapper 1.4.1 and the latest 1.4.2. clean install of 1.4.2.
i've just stopped using quad masking for my projects, but have a really big festival gig coming up next week where masks inside the quad will be needed and i want to make sure that I can use it for this show without issue.
if you have any insight as to why this is happening, please let me know.