HELP trailer sway almost killed us!

Thanks everyone for your help. I'm leaning towards a problem with the trailer brakes and a hitch that was too high. The load I think is pretty balanced. Most of the "open" storage is towards the front of the PUP and the fold down kitchen is directly over the axle. We always travel with an empty water tank. Also this happened on our previous vehicle when the trailer was level and it had a different brake controller. So, it has occurred on two different vehicles with two different brake controllers, leaving the common element or variable being the trailer brakes. Again everyone thanks for all the advice and help. Trailer brakes are being check now by the dealer. If they checkout good, then I'll go back to the place that installed the controller as well as getting the correct height hitch.