If you use the Learn function on a board, and it seems to ignore an certain part of the memory map that you know for sure is a certain type (e.g a section of the memory map allocated to RAM), run the appropriate test on that area. Bet it will detect a problem with it.
I recently performed a Learn on a board and it failed to identify an area I knew to be RAM. Turns out that the RAM had stuck bits, which must have made the Learn function think it was something other than RAM. So now I understand that the Learn function can also be used to spot problems with a board.