First time posting, thanks all for the great site and advice!

We completed a remodel of a 100-year-old home last summer. Interestingly, the kitchen sits over the garage and the subfloor of the kitchen/ceiling of the garage is a 5" thick floating concrete slab. Same slab approach they used in all the bathrooms.

We wanted to install hardwoods (previously there was tile). The vendor found a 1/4" thick glue-down oak product with the same narrow width as the original oak floors throughout the remainder of the home. I'm honestly not exactly sure of the terminology, but I believe it is an "engineered" product, but not like a laminate (they installed each individual board, then sanded and stained like a nail-down product). They glued the wood directly to the concrete rather than putting down a plywood subfloor as they didn't want to create large step-up transitions with the adjoining rooms.

Well, about 6-9 months after install we started getting significant cupping. Then, we started getting multiple soft spots where the hardwood would compress/pop when you stepped on it. The main contractor and the flooring subcontractor said they see this all the time, and they would just use the Dri-Tac wood repair system. No problem. They drilled holes, injected the Dri-Tac glue (they had to inject A LOT of glue), and then told us to stay off the floors for 24 hours. When we came back 24 hours later, however, all of the areas they glued had popped up. Some of the boards were now "only" 1/8 inch higher than the surrounding, non-repaired boards, but some were 5/8" higher. See attached photos.

The contractor and flooring sub said this was just temporary because the glue has water in it and that the floors would settle back down to normal after 24-48 more hours of drying. One week later, they haven't budged.

So now we have multiple significantly raised areas in the middle of our floor. The contractors initially said they could just sand them back down, but how do you sand 5/8" of elevation on a 1/4" board?

Has anyone ever seen this with the DriTac product (the label does say some temporary cupping can occur)?

Any idea how to fix this?

Any idea why the floors cupped/popped so soon after install and how to keep the rest of the flooring from doing this?

Thanks!!