That's the issue with KYM's stupid image recompression algorithm. GIFs are usually optimized to reduce their size by removing pixels that are of the same color on the next frame by making them transparent, this can cut the size down 3-4 times depending on content, and it works fine everywhere…

EXCEPT KYM, which deems it fit to re-optimize the image. It does so by un-optimizing every frame, then re-optimizing it with its own algorithm. The problem is, that the algorithm is lossy, the more optimized the GIF was from the start, the worse the result will be.
I've already raised this issue WHOLE 7 years ago

https://knowyourmeme.com/forums/report-problems/topics/35399-kym-downgrades-gifs-on-upload-increases-filesize-while-doing-it?page=1

Without any satisfactory reply from the staff.

It works without bugs if the the global optimization (removing rectangular parts of the image that don't move, GIF has one single palette) was used. If local optimization (removing every reoccurring pixel, using own palette for each frame to maintain quality) was used, then you may or may not see the stuff you've posted, as the lossy compression has unified the palettes of individual frames which results in shifting of the color indexes and transparent parts becoming nontransparent black.

Not only does KYM breaks the GIFs, there are also no checks if the re-compressed image smaller or bigger than the original.
In fact your own "Jimmy Yelling at Howard" GIF originally was 4.8 MB, but the KYM "optimized it" to 5.0 MB.

It couldn't even be argued as "saving space gone wrong" issue, as the site KEEPS BOTH VERSIONS ANYWAY, you can see the original by clicking on the re-compressed variant on its own image page.

I've brought this issue up several times over the years, and nothing was done about it over the last 7 years, so I don't think anything will ever be done.

In fact this is the reason I stopped posting GIFs of my own making after the site refused to accept my own well-optimized 4MB GIF because it was over 6MB limit when optimized, and the site checks THAT version for the limit instead of the original.