Not that I doubt what your saying but it doesn't make sense to me. If you set it up in the beginning then you would have set it to lock the brakes and then back off a bit. If it worked then it should work now.
Also, there should NOT be any relay in the wire that goes between the brake controller and the trailer and the supply that provides power to the controller doesn't need any relay installed.
Keep in mind that the voltage going to your brakes is variable and there's no way a relay will do that.
If he installed said relay then it's wired wrong and your not getting proportional braking.