CliffordK

I've had something similar happen to me.

I was pushing it up hard climbing a rolling hill to a stop light when I got a light change. I hit my brakes and the bike went flying.

It was a combination of issues including forward heavy from the hill climb, and a sudden hard stop. But in post analysis I also discovered that I had reversed the brakes, so most of my bikes had Right-Rear, but that particular bike had Left-Rear. And, of course, my own fault.

So, at the next opportunity I swapped the brakes around, and started paying a bit more attention.

I can't say for sure if that was the cause. I usually modulate my speed with the rear brake, but at times will also grab it hard, with more finesse with the front.