Mickmeister I looked up the rear derailleur specification and the Shimano derailleur being used does not have a clutch on the jockey wheel chain tension take up arm. Derailleur bikes are terrible on rough terrain for shifting when hitting bumps. The derailleur manufacturers solved this problem by putting clutches on the jockey wheel tension arm assembly. The clutch does not let the derailleur shift unexpectedly when hitting a bump. An example is the Shimano Shadow MTB derailleurs with clutch. When the clutch is engaged the derailleur will not shift on every bump. Mountain bikes, gravel road bikes, and any bike being used on rough terrain will benefit from this derailleur clutch technology. The shifting can even happen on paved roads if you hit a big enough bump or pothole. I hope this helps you figure out what is going on. If you are going to be riding hard in the rough I would upgrade the rear derailleur to a clutch design. You will be much happier with its performance.