I'm on CC 2017 because it usually works, until now...
when i animate a mask then go back through the key frames the mask is not where i put it... it will be cropped in past the blue line, then once the glitch is present, moving the blue line only moves the overlapping black area slowly. I don't know if anyone else has seen this, because I want to uninstall this program after seeing this.
How do i fix this, quite using Premiere?
Can you post a screenshot of your effects controls panel with the affected clip. Some effects and their stacking order can affect your expected results with masks. Try nesting your clip before applying a mask.