Playback is correct in MS4 source file, but distorted on upload to Musescore.com

I uploaded a complete orchestrated choral score (created in MS3) to the MS4 platform, and reset the audio to the improved MS4 soundfonts. After a few adjustments, things sounded great within the MS4 program playback (I cannot attach the source file because it exceeds the 4MB limit). I was able to generate a perfectly acceptable MP3 file with it (also too big to attach here). I was so happy!

However, upon upload to the "cloud" and playing it from Musescore.com, the sound becomes completely distorted. Individual notes are sustained indefinitely, rendering the playback unbearable to listen to within the first couple of pages. Furthermore, the piano reduction for the orchestration, which was muted at the time of upload, can be heard prominently. There is also heavy accenting of notes that I don't hear within the MS4 program playback.

Here is a link to the cloud-uploaded piece:

https://musescore.com/user/29381772/scores/11557498/s/JjaiJN

For what it's worth, I think part of the note-sustaining issue may be due to my frequent use of the "fade out" articulation. I use this extensively in my MS3 transcriptions (usually in hidden form) to provide a subtle emphasis to various notes (accent articulations are usually too strong-sounding), thus improving the audio quality. It seems to me that the erroneous sustaining problem starts on notes where those fade-out articulations (hidden or not) are found, although it does not occur with every note articulated that way.

At any rate, I must continue using MS3 until such time as I can consistently achieve correct playback on Musescore.com with MS4 source files. Not quite there yet; I'll wait for the next release to try again....