Sweden Yachts draining problem

Jan, how are you ? Any progress on SY getting back up again ?
We have just come back from the Chesapeake Bay where we left the boat for the next year. She is up on the dry in Rock Hall. We had a fantastic 8 months of sailing with very few problems, and many compliments for the beautiful design.
I had one interesting problem : when my black water tank forward was blocked, I managed to open the blockage by taking off the hoses from the tank in the saillocker (the blockage was behind the open/close valve) but then the contents of the black water tank went into the saillocker. I thought they were flowing straight to the bilge so I could pump them out.
However, instead all black water ended up in the two floorlockers in the owner's cabin (one under the bed, the other where the speed and depth instruments are mounted). There was nothing flowing into the bilge, so I had to bail everything out manually.....
Should there not be holes that connect those two floorlockers in the owner's cabin, with the deepest bilge over the keel ? If there is such a connection, how can I reach it ? I have not been able to find anything, so de-blocking was impossible.
And related to that, a lot of black water got stuck in a pretty big central space between those two floor lockers (In front of mast, below floor). I could not reach it. Later, when the boat heeled over, it came streaming out into the lockers again and the cleaning had to start again.
Can you help to solve this mystery ?
Best regards,

"I know some boats have had this problem and the water should end up in bilge if the drain holes are drilles and not clogged"