MuseSounds appears to lag behind default instruments for large scores.

I am working on a score and I decided to test uploading it to Musescore. I have worked with the MuseSounds instruments before and have not had any issues with it previously. However, around 2/3rds the way through the score (starting at section #12 I think and is most prevalent at #14 and #15), the MuseSounds instruments appear to fall behind the default drumkit causing the score to sound... not great. It's like the percussionist suddenly lost their sense of tempo.

But when I upload to the site without using MuseSounds, this problem goes away entirely (and introduces some new issues, but that's besides the point). The problem also occurs if I try exporting the score to wav with default settings.

Here is the score with MuseSounds:
https://musescore.com/user/1214651/scores/9837289/s/GAK--Y
And here it is with default instruments:
https://musescore.com/user/1214651/scores/9837094/s/_AuMzM

I have also uploaded the Musescore 4 file which does not have this issue whatsoever on my machine. Make sure you have the Muse Keys and Muse Strings packs.

Also, as a separate (unrelated?) issue, these weird black bars show up in both versions of the uploaded score.

Any help would be appreciated. I don't know what caused this issue and I would like to continue to use MuseSounds if possible.