Looking for documentation for VAX-11/730 ENKCC Diagnostic

Hi all -- The VAX-11/730 we have running here at the museum has developed a fault that occurs only sporadically, usually days apart. Running the complete diagnostic suite for the better part of a week reveals this: SECT TST ERR EXP REC OTHER MSK MODULE ENKCC 33 08 000000FF 000000DF N/A FFFFFF00 M8391 M8728 Re-running only ENKCC, this error is repeatable (though it still takes a couple of days for it to occur). It helpfully points out the MCT (M8391) and memory boards (M8728) as possible causes; we have spare M8728s and I've swapped them around with no change in behavior. I have a spare M8391 in my own collection but it fails in a completely different way so that's not much help. I cannot find any real documentation for ENKCC so I don't know what TEST 33 is doing, nor what ERROR 8 indicates in this context, though it seems we're dropping a bit somewhere :). Anyone out there sitting on a pile of 11/730 documentation? Thanks as always! - Josh