Hi, I've had the same problem with my T300 lately. I've managed to fix motor so I thought about sharing some pictures and instructions about how to solve the problem with calibration due to poor glue quality on the shaft.
https://drive.google.com/open?id=1ZYPQW2lONKaFXNFjZU9Rx0JQS5eaNCWp
Hope it will help someone.