Keystone will resist to no end, and visiting dealers,calling,emailing,or writing letters to Keystone will probably end in frustration. Keystone does not vacuum bond their laminated floors and walls, they pinch roll them, and they skimp on the amount of aluminum tubing in them.
We had a 2013 Keystone Passport. Although the floor never failed it had a lot of flex and made noises that drove me crazy. When I would be sitting outside and someone was walking in the rig, all you could hear was creaking / cracking wood and the seams between plywood grinding together. It used to make me go bonkers. I did a lot of non destructive investigation and found the aluminum tubing in that floor to be on 4 foot centers. It never developed soft spots or delaminated though, was just annoying as hell.
Most dealers will not take on such a repair. The entire rig is built on top of, or attached to the floor, including the wall panels. The correct repair is return it to the factory and replace the entire floor which Keystone is most likely not going to offer. Its essentially rebuilding the trailer from the frame up.
Perhaps its time to go visit the guy with the Esq. after his name? Probably your only option although not a good one. May be expensive with no good results.
Another option may be epoxy injection. I have done a few sidewalls to fix delam with good results but have never done a floor. A floor is a different animal due to the foot traffic.