This boulder will catch your eye if you walk up the hill of Isatis. It is a huge block with a looooong traverse on it. Luckily for La Rampe Finie you only have to climb half of the traverse and exit by a friendly mantle.
Rain sucks, but broken holds suck even more. Remember, never climb on wet rock in Fontainebleau.
The sandstone becomes brittle, and pulling on it will ruin classic problems. Drying it doesn't help, because it's still wet and weak inside.
All you can do is wait for better conditions.