Hi Dirk
You wrote "First, I thought the boat yard did a bad repair job of one of the delamination parts they have been working on. But when studying it, it became clear the new damage occurred in an area where no repair has been made by the boat yard, although they repaired the areas around it."

That is what I was referring too...When they did their repair the damage was done, the foam was changed once it hit its heat distortion temperature...this often causes the foam to "out gas" When in a cool environment out of the sun the laminate appears normal and the problem is undetectable...when you bring it out into the sun and the laminate heats up, gasses expand and distortion of the panel takes place. This may or may not be the cause of your problem...but it does exist...

Regards,
Bob