Long story short bought some Elka flooring last year at £37 2m so wasn’t cheap and stored it in the room I was laying it in for 2 months , when I opened the packs the planks bent like bananas from end to end , told the shop about it and they said it would level out so layed the floor on good underlay and the floor was flat , ever since laying it it feels like a trampoline in places , and feels different as the room changes temperature, are the planks faulty ?