After Scrubbing in Sequence reverts to back to another frame

[jMarc]

I am trying to scrub on my sequence to set keyframes for a mask. However, when I release the mouse while scrubbing it goes to another frame. However, I cannot figrure the pattern or reason why it keeps reverting back to the other frame. I'm sure this is a preference or simple issues I'm dealing with but I couldn't find anything obvious in my setting or online.

Here is a video with an example.

Thank you all!

Joseph

[jMarc]

I realized that it has something to do with my proxies. But I cannot figure out how to match up the frames of the proxies vs. original files.