My exdh bought a load of engineered oak (4mm) to lay in our hallway/kitchen but whilst we went through a couple of crises it was all unboxed but stacked against a radiator which was on all winter. The planks all warped, the oak side shrinking significantly against the ply. Almost a year ago now I restacked the planks away from the radiator in a cooler room, turning them the other way up in the hope that the sheer weight of them would press down on the warp & flatten them again. Sadly this didn't work. I think they're completely unlayable now. Is there anything I can do to make them 'relax' back flat again.