Looking at the "Melody & Rhythm Control" section under "Cherry-picked"... the rhythm control is weird. In many of the examples, the generated music clearly has a different BPM from the reference. But the model seems to still be trying to align the notes in units of time (rather than beats), so the notes get desynced with the beat. The model then tries to cover up the discrepancy and make it sound like syncopation, by emphasizing or de-emphasizing or outright altering notes, but it doesn't work very well.
Maybe conditioning on the BPM would help?