Let’s put this into terms we can all understand. You sit down in your favorite chair and turn on your reading lamp. There’s a dull orange glow. You change the bulb with no improvement. You get out your DVOM and the receptacle shows 80 volts. Do you re wire the lamp hoping to improve the bulbs performance on less than required voltage or go to the breaker box and find why you have low voltage?
As for trying to help; there’s multiple threads here on the subject. The latest provides ACTUAL voltage readings from multiple vehicles, under driving conditions rather than how things “ feel”. The facts are what matter. The effort made by that poster to provide solid information matters.
If 80 volts is
supposed to be coming from the receptacle and the bulb is dimmer than it should be then you look at the lamp.... That's what you're missing. The system will work fine on good trailer wiring with the reduced voltage, in fact it's still rather aggressive at low speeds.
The reduced voltage at low speed is absolutely how they intended it to work, and why the dealership said no issues. The issue is that the controller cannot overcome any wiring issues with that reduced voltage, unlike an aftermarket controller. The aftermarket controller is just masking a wiring issue, while the ITBC can not.
Think about when you're driving and coming to a stop, do you apply more service brakes as you slow or less? You apply less, and that's what the ITBC does.... if you
NEED full voltage at low speeds then something is wrong with the trailer brake system (wiring/magnet/shoes/etc). Fix that system.
You're blaming the ITBC because it's different, and easy... that doesn't actually mean it's the issue.
In this thread the OP has had the ITBC checked and it was found ok. He also stated that the trailer worked fine at one point in the drive, but then got worse. That's sounding like a trailer issue. It's a new trailer, which should be trouble free, but we all know how that goes with trailers. The likelihood of a loose connection, bad ground, etc is pretty high on a new trailer.