"Hallow Knock" Sound


New Member
When pedaling, my bike has started making a "hallow knock" noise. I don't feel anything obvious that bad things are happening.
The sound is coming from the right side of the enclosed motor/pedal.

I stop and start peeling, I shift up and down, and it starts, stops, or continues. I makes the noise in all different positions of
the crank.

This happened on a Bulls Hardtail MTB Bull's loaned me while they replaced the frame that snapped on my MTB. The noise
became more often as I used the bike.

Now I have my MTB back and the same thing has started. It NEVER did this before. Its a "loud hallow knock" that has become
super annoying.

My MTB is the E-Stream Evo FS 3 27.5+

I'm hoping someone has experienced this and learned the cause and can share the solution with me.