If there is abnormal sound, first check whether the inertia wheel rubs the bracket and the belt to run off, if not, check whether the magnet is damaged. If the magnet broken will appear abnormal sound or immovable phenomenon, this time you need to replace the magnet. If you need to replace the magnet, please contact service2@thinkrider.com  and we will provide you with a new magnet. You can learn how to do it in the video below.
A1 replacement magnet video: https://youtu.be/J4ZrsTRm2MU