That is a problem called a slipping motor pulley that sometimes happened on the EEW Nano 1.0. I've addressed this with the EEW Nano 1.0 by adding little grooves to the motor shaft to prevent the pulley from slipping. That said there is an easy fix for the EEW Nano 1.0. Here's a video that shows that fix. kzfaq.info/get/bejne/oZtxmd2BqbTcdp8.html