Should TT Brakes Lock Up

I've seen plenty of threads on Ford brake controllers not being able to lock up the trailer brakes and even more threads on weak Lippert trailer brakes. I believe that the OP's problem is most likely with the trailer, as is mine. On the same 2012 F-350 our first camping trailer with 2 3500 lb. Alko axles would lock up the brakes if the controller was set too high. On our present flat bed trailer with 2 7000 lb. axles, the trailer brakes will lock up if the controller is set higher than 3.5. On our present camping trailer, a short fifth wheel that weighs 9400 lb. loaded ready to go, the brakes have never locked up (all on the same truck with the same controller.) In fact new but broken in, the trailer brakes would barely slow the combined rig. I firmly believe that the axle makers (Lippert in particular) are making and recommending cheap inadequate brakes to keep the price low so they can get the business.