I've noticed that when I'm (Ctrl+>) to process the next frames, if I need to make a correction and do so before it finishes propogating and wait for the bar to turn from green to yellow, it locks up, makes crazy changes to the mask I didn't ask for, and starts glitching thr programs on the taskbar in Win10.
A warning dialog should appear if you attempt to draw a stroke while propagating frames, advising that strokes can't be added until the current frame has finished rendering. And AE should not be locking up. I might have better luck reproducing what you’re encountering if you could post a screen recording? Thanks.