Zauberlehrling on Nostr: Starting to feel some grinding/vibration - but I'm not sure where it is in the drive ...

Starting to feel some grinding/vibration - but I'm not sure where it is in the drive train. It's not bad, only noticeable at lower cadence. This is a refurbished model I have had for 1 years, don't know how many hours/miles total it has on it.