Very likely the wood handrail
If you tie things to it or walk around on it, the screws will eventually work or even break and a leak develops.
We have had this twice on our 2005 D34.
You have to dig out the screws, get some sealant under, and put in more screws if necessary.
We used to tie our rubber dinghy to the rails….but no more
Jeremy Vines
The membership association for owners of Dufour Yachts