A lot just "depends".
As with many trailers, they do better with a little tongue load than with tail load, so high speed and tail load and they're just wicked. The spring couplings are simple and work well, but have a little less control than more rigid couplings.
I do cargo, not kids. I've flipped my trailer multiple times. Usually riding light, but I have flipped it a few times with loads. Usually hitting curbs, curb cuts, or potholes, often "at speed", although not necessarily at extreme speeds.
I've had my trailer flip me once or twice.
