Brushed mask jumps up/down & left/right if the paintbrush is close to the edge of the photo when the mask needs to be moved.
I'm editing a night lapse from a programmed head and have been moving a mask frame by frame but run into aforementioned glitch and it makes it impossible to place the mask where I want it to land. It would be good to able to chose where the paintbrush is located within the mask.
Sorry to hear about this. Have you tried turning off the GPU option from Lightroom's preferences? Go to Lightroom > Preferences > Performance tab > Uncheck "Use Graphics Processor" > Restart Lightroom.