My dashcam is also playing up. I have a Dec 2020 M3LR. I have recently purchased a new 1TB Tesla USB/SSD. I previously had a 128GB Kingston Thumb drive, which just plugged in, I was able to format, and both sentry and dashcam were being recorded for the months of October and November. The dashcam seemed to only keep for 24 hours, and then would be overwritten the next day. Recently the dashcam stopped recording all together , so I got the Tesla 1TB drive from the store. I had to jump through the following hoops to get it to format:
1) Soft reset using the thumb wheels.
2) select Format USB in the Safety menu five times in a row before the dashcam icon had a solid red dot.
I only picked up the car in September, so it is possible the car had this issue already. Is there a USB recall related to this?