Factory tow brake’s gain is at 10

[Campingnownthen]

So our 2016 Silverado 2500 HD Durmax has factory tow brakes. When I set it on 10, you can barely feel the trailer brakes engage. I think they should be locking up at this point. We are towing a brand new 5th wheel but this was also happening after taking our 2014 5th wheel out several times. I’m thinking it is a truck issue but not sure if there are things I can check first before taking it to the dealer or if this is can only be fixed by a mechanic. Not sure what other info you might need that would be helpful but any info would be greatly appreciated!