When the boat was repaired could something like acetone used to clean the boat run along the inside of the skin and do its damage slowly. I spilt a rust retardant on my leather car seat several months ago. I wiped it down with a damp cloth and it looked clean. Three weeks later the spill had melted right through the fabric and a month after that it was even worse.
Were the hulls sealed or tight?
Whatever, I feel for you. I would be gutted!