You state
"I was thinking that any water that enters the boat would be channelled to the bilge pump and evacuated, but maybe this is not the case?"
That is definitely the case with our 2015 R21EC, all water ultimately migrates to the rear bilge pump area.
It appears you have two problems, a rainwater water leak and something obstructing the water from flowing the full length of the bilge. Both should be addressed.
A garden hose selectively aimed at likely locations on the deck while someone is watching in the V Birth area for leaks may give a clue as to where the water is entering.
As for the bilge blockage, that will take lots of poking around with a flashlight and for hard to access areas use you camera phone with flash.
Keep us posted on your progress.