Had a similar issue with our new 42' Expedition. It was all over the place. Got it weighed and inflated the tire according to the tire manufactures graph loaded for maximum weight.
The tires were way over inflated. Airing them down per specs made a huge difference. Also had it aligned due to it pulls right. That didn't help. I assume it's due to the crown in the road in the right lane. So I have a constant left pressure on the steering wheel for the most part. But the fighting is gone.
If your coach is new adding steering stabilizers " might" void your chassis warranty. It states this in my Fleetwood manual. But there may be things fleetwood would need to prove first before voiding it.