It's not just you... single axle trailers are notoriously sensitive to steering input. Use very minor corrections and go slow, slower, slowest. When towing my 10' cargo {motorcycle} trailer behind our Class C it is a challenge as I cannot see it in the mirrors until it starts to swing wider than I usually want/need.
If I angle the rear camera down to see the ball then I lose most of my view of the trailer - raise the camera angle for a better trailer view and I cannot see the ball. Might be time for a second camera.
:S