Onewheel GT issue

Hey yall! I have been riding for about 5 years and have about 13k miles under my belt. My GT has about 3500 miles on it and I have treated it very well compared to my first 2 boards. I think that I am very well versed on my board’s capabilities. A couple weeks back I was taking a 90 degree turn on a sidewalk and slowing down feom about 12 mph to about 4 or 5 mph to turn. I have made this turn a billion times without issue. All of the sudden during breaking the board gave way on the back end and shot out from under me. I landed on my feet, picked up the board and jumped back on (board was still on). I made it home with know issue after but thought it was very weird that that happened. My very next ride, i was taking it pretty easy on the board in case it did the same thing. Made it about 8 miles with no issue and then going 17 mph on a sidewalk with no real obstacles or strain from the board it did the same thing and gave way on the back side of the board and it shot out from under me. The board was still on when I picked it up and I gingerly rode it home for about 4 miles not going over 10 mph. I had the app out and was watching it on the ride home and the meter that shows you how hard you are pushing the board was constantly in the red even though I was riding super easy on it. I assumed it was the bearings being old (3500 miles on them) but when I opened it up today, the bearings look and spin fine. What else could be the issue? Controller? The battery has been babied too and is just as good as day one. Has anyone else had this issue and fixed it? Thank in advance!