Mask Path 'sticking' on certain keyframes

Hello, I had the same problem and I managed to fix it by deleting the following keyframe, and keeping the same mask as before just by changing a few points (I think I had added a mask point which would have caused the problem).

I've been dealing with this issue too and I've found the exact same thing that Grant mentioned - it appears permanent and maybe even almost infectious, the more you try to correct it the more errors accumulate. Has anyone figured out any way to salvage the work put into keying a shape, once it's already done? I haven't, but maybe someone else is more lucky. 
Could the issue be tied to errors accumulating in the project itself as you work on it? Has anyone found a way to at least mitigate the frequency that this error occurs, if not to fix it?

I f-ing hate this problem. Bought premiere 2020 and still the same? How come they don't solve this issue?
Took me 2 hours to precisely mask a figure and when I checked it back it was messed up because of this.

This is indeed a problem I've been experiencing for years across multiple versions of Adobe Premiere Pro. It is not fixed by this date, and I just recently decided to google to see if anyone else is experiencing this issue of keyframes holding on masks and not blending. It has nothing to do with time remapping, but seems to be an error in Adobe's masking function. I'd love to see this issue addressed and fixed someday as I have spent many hours messing with keyframes, deleting problem keyframes, redrawing masks, undoing, and basically every other "fix" you can think of. The sad part is, the problem only worsens as you attempt to remedy the issue. More keyframes start holding their mask postion and snapping abruptly to the next value once the playhead reaches it on the timeline, and eventually, it seems that entire sections of your clip will hold their keyframes as you fight with this issue and try to fix it. No matter of restarting your program, computer, importing the sequence into another project (yes the issue persists across projects), will fix this infectious error. 

It's possible there is some radically difficult and hidden way to fix this frame holding problem, especially if you've spent hours creating your mask, it might be worth trying to save.

But if you've spent less than a few hours creating your mask, I recommend to stop trying to fix it. Cut your losses, and start over by creating a new mask. You'll spend more time trying to fix the problem than it will take to just make a new mask, I promise you, from many hours of first-hand experience, I know.

As a side note, I'd try to distance yourself from the infectious issue as thoroughly as possible, delete the clip from your timeline, maybe delete that sequence and remove the video file from your project and rename it in your file browser before importing it again so premiere thinks it's a different file. You don't have to take these precautions, but you can if you're paranoid about the problem replicating.

Hi there, I had been running into this problem, as well.  I'm not sure if this will apply to everyone, but I found what the problem was on my computer.  If I accidentally created a new point on the mask, and then hit the keyboard shortcut for undo, it would somehow stop the inbetween.  Simply hitting undo a second time seems to fix it for me.  I hope this helps others.

Hard to tell from the images but on image #2 it looks like you're on the keyframe rather than 1 frame before it. Are you magnified in at 100% in the effect's control panel timeline? Otherwise you'll only get an approximation of where the keyframes are relative to the playhead.