Keyframe Animation Stuck

I'm editing a video in which I'm placing a mask over the person in it in order to blur the background. Since the mask is moving, I've set keyframes, but the issue is that in between keyframes, the mask should be animated to move from the position of keyframe A to the position of keyframe B instead of just jumping to the new position of keyframe B. In some cases (there doesn't seem to be a trigger), after mask animations work for a few keyframes, they suddenly stop, even when working in the same clip within the same sequence. When switching to another clip in that same sequence, the animations work again. It seems as if there was a limit for the amount of keyframes I can place before the animations stop working. Does anyone have a solution for this?

I'm working with:

macOS Mojave 10.14.5

Adobe Premiere Pro CC 2019 13.1.2 (Build 9)