PDP 8/e, RK8E Weirdness

Earlier today I did pull the MOS memory, and ran all of my tests, and it didn't make any difference. It failed the same way, consistently. I think that I could cram all needed onto one Omnibus, but it'd be tight...I think that 17 of 20 slots would be full...and I usually like to have a little room between the boards just to prevent anything from bumping together. I can't believe that DEC didn't use card guides to hold the boards in place. I have not pulled the Omnibus backplanes out of the machine and checked the foam underneath. Although, the machine does run rock solid in all other aspects. This machine is very "original", and hasn't been messed with much at all since the day it was new other than DEC maintenance during the years it was in production service. Maybe I need to do a "housecleaning" on the machine, and pull it apart and clean everything out. As for the foam, if it has deteriorated, is it something that needs to be replaced, and if so, what should it be replaced with? Thank you for your suggestion to slim down the bus, and see if that makes a difference. Having less loading on the bus could change timing of bus signals in such a way that things work...especially in light of what David Humphries mentioned with regard to a spike in the signal that clocks the data in the current address counter. Rick Bensene