usually, there's water intrusion into the bottom of the bunk door and the hinge/sill area. both have to be rebuilt. some order a new bunk door from the factory but some build their own door and rebuild the sill area themselves.
you have to have some carpentry skills though.
i know this is too late but did you look under the hinge area, into the storage area underneath?
also, for it to go that quickly, there had to be some bad wood, in the hinge area, when you bought it.
i'm sorry to ask this but i think prospective used hybrid buyers need to learn from your experience.
this is a big reason why we decided to buy new because good used hybrids have to have been maintained well and closely.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC