leveling over chipboard

I've been trying to get my 22m chipboard floor (on joists) flat in two rooms and a hallway of the 1st floor, so I can lay a floating click engineered floor. There is one high spot left in the hallway , which is partially over a steel I-beam which i think is why board is bent out of shape. I...

Had bi folding doors installed earlier in year, pre COVID. We lifted the inside floor by installing a DPM, sandblinded to level, overlayed 100mm insulation then covered with 22mm caberdeck flooring. As the DPM covered the bottom of the door I didn't take a lot of notice as we installed the floor...