While calibrating and testing the new design, the vibrations from the motor were quite annoying.
I did a little bit of research how to reduce the vibration from the motors into the frame and found vibration dampers on eBay and Aliexpress. Since they are quite cheap, I ordered 3 of them.
These dampers are very simple: a rubber ring is melted between two shifted junctions for the motor and the holder.
The noise reduction is amazing, the plotter runs very quiet even while fast jogging to a certain position. Definitively worth the money. However I could not see any difference in accuracy yet.