Hi Barker and Davide,
Penetrating Epoxy would be the best "treatment" for this condition.
Check out this link on CPES Penetrating epoxy.
I'd suggest thinning out the epoxy with whatever the recommended solvent for CPES
Set the area of your board that does not appear to have "soaked up" sufficient epoxy when wood layer was put on during manufacture as level as possible.
Mix and thin the epoxy for the longest suggested cure time (gives the penetrating epoxy the most "soak" time to ensure max penetration).
When the CPES has fully cured, sand back until you just start to see some of the white from the thin layer of paint begin to show up on your sanding pad.
I'd recommend wet sanding by hand here.
If the wood layer (only a few tenths of a mm thick, like heavy paper) didn't get enough resin when your board was built, this is about the best way to get more resin to the wood and stabilize the outer layer so moisture no longer causes it to swell and shrink.
Hope this helps!