As for Belt twisted issue, I have not seen issue like that. But one thing I would like you to check is if freewheel is properly “free” or not. If freewheel sometime does not work well, the belt will have unbalanced tention between top and bottom, although this is just my assumption.
I have had a kind of cracking sound issue in the past after riding my Strida under rain few times. My recommendation for this issue is to loosen screws from where the sound is produced, and tighten with proper torque, on top of rubing proper position(s). Using torque wrench is best.