When the game lags on client-side or server-side midi tracks become desynced for the rest of a song, and becomes more and more noticeable on songs with great amounts of tracks.

The easiest way to reproduce it is to play a midi with 10 tracks+; but, you can also intentionally lag the game out to cause it as well. It becomes more of a problem on larger modpacks due to instabilities.

Of course, the expected behavior is for it to sound good; but constantly resyncing them would probably be taxing on the network so I'd recommend resyncing maybe after each bar or two.

Is a single player enough, as in, the desync happens between tracks and not between entities? Does the track plays properly without lags?

I think what's happening is that it starts playing tracks one after another starting with #1, so the more tracks you have the worse it gets, I've been experiencing sections of songs starting multiple seconds before they should in a relatively lag free environment.

Can you add a good example for me to reconstruct?