We have a 2021 Highland Ridge - Open Range stick and tin (conventional) trailer. It has a 3/8” walkable roof deck, although ours did not come with a ladder. I noticed the other day from my stepladde...
Get it fixed NOW!! If it looks like that when it is new......You will never be able to sell it when it has some years on it... Agree thay the OSB has swelled due to moisture. This weakens it, and it is a one way trip down a wrong way street from now on.