Last night was the third time I about poo'd my pants. I need to figure out what the issue is. My trailer has come off the ball now 3 times at highway speeds. The trailer has surge brakes and the coupler is not marked but accepts a 2" ball. I tried a 2 5/16" ball and it was to big. I don't know a lot about surge brakes but it looks like the coupler is all one piece and part of the hydraulic system. First time it happened at 55mph, I hit a bump on the highway and the safety pin bent and the trailer popped off. The second time the same thing happened. I bought a new pin and last night it came off again at about 35mph on my exit. This time the pin is still in good shape. So with the Pin in it does not take much pressure using a jack to lift the trailer off the ball. 2 5/16 is no big and 2" seems to be to small. Any ideas?