I voted “once”, because I couldn’t remember for sure, but I thought there must have been something. Now when I have given it some thought I recall several episodes, but not all of them qualify as endo while/due to braking.

I have endoed several times due to crashing into things or getting front wheel locked in a hole or similar.

Once was when I as a kid I was happily pedaling along a path that led over a wooden bridge over a canal. The bridge was picturesquely curved so the mid part obscured what was behind it. Behind it, as I soon learned, was... pretty much nothing – upon reaching the middle of the bridge I saw that the other side was destroyed. It was too late to brake, I just continued on my way, hit the other bank of the canal hard with my front wheel and went over the bars. Nothing serious, as slightly bruised nose and a nosebleed for a couple of minutes. The bike was alright too. Later I learned a car had crashed into the bridge from other side the night before. Apparently nobody thought of fencing off the site in any way.

Another time was when I crashed into a parked car. Don’t ask me how, as I’m at a loss still to this day; I only remember that it was raining hard, and the hood of my raincoat was sliding onto my eyes and I had to push it back up all the time. So one time I pushed it up and saw a car’s rear end in about 2 m from me. Went through the rear window facefirst. Again, no major injuries, just a nosebleed and some minor cuts on my face. The bike had bent fork, which I later bent back into shape myself. Had to reimburse the car owner for the broken window too.

I’ve also did that foot getting stuck between the wheel and fork thing mentioned here before.

The last time was some 3-4 years ago. I was at a friends place; his house is on a river bank. I was going down the grassy slope towards the river, an open beer in one hand, steering and pressing lightly on the front brakes with the other, when I hit a small depression hidden by the grass. No damage whatsoever, not to myself nor the bike, and I even didn’t spill the beer