As the OP I have gained valuable information from this thread so I thank everyone for their contributions.
Our dead dinghy
was PVC and never had a patch on it anywhere and never deflated.
The PVC was no problem but it was the glue on some seals
We had some very high temperatures in Greece
and the glue just filed totally in a day or two. Parts
that were glued on just dropped off and the glue around the end cones and transom failed causing the problems.
I presume the same type of glue is used on other dinghies no matter what material they are made of.
Up to that point I was very satisfied with the dinghy.
Given the choice I would have preferred Hyperion but it was 3 times the cost of PVC and the dinghy was guaranteed for 5 years.