With 22,000 kms on our 2015 i3 Rex and about 1,300 kms of Rex use (and a good portion of that coming in the last 6 months after coding), the motor is still near new and breaking in! How much use does your Rex have on it?
I wonder why they would be looking in the cylinder?
Perhaps they were looking for something that they were expecting to find.
Did they pull the plugs and look inside with a scope. I have heard of techs cross threading spark plugs and then trying the drill and tap out the hole to put a heli-coil in. That can be a source for shavings.
Did they find metal shavings in the oil?
Where these steel or aluminum shavings? Knowing that could help determine where the shavings came from as this could be something that others might experience.
2015 i3 REX