based on our experience, this looks like a faulty controller and/or LCD Display. Please connect with Sondors to resolve the issue. firstname.lastname@example.org
If you are out of warranty (which you aren't) consider buying a new aftermarket Controller&LCD combo for around 100$ form https://sierraebike.com (this will void your warranty - if you are installing it)
We on the Forum are really sorry that you have made this experience. I hope the Sondors Customer Service will resolve the issue asap.
All the best,