Tartuffe,
The pic shows where the inner skin meets the outter hull at the gunwale, next to the transom. It appears the 1975 hull had three piece construction. Outter hull, inner skin which matches the outter hull shape and included the original floor, and the gunwale cap. It looks like weave that isnt filled or smooth with resin and only looks like its an issue in that one spot. With force Im sure some layers would separate about an inch or two down and weak in that area. Here is the same pic edited. Ill try and get a better one for you.
Thanks again!