Scooba 450 idling in place

My Scooba 450 just idles as in the video here. It's been doing this for 4 or 5 times already but a factory reset (pressing room + info buttons) solved the issue. Not today: what could be the problem? Everything is cleaned, the bumper moves freely. I've been using it very seldom until one year ago, then I started using it daily to clean a small room.

Thank you for your help!