SWTPC 6800 issues again

Hey guys, You might recall a while back I was having issues where I'd have to power up/power off multiple times before I'd get the 6800 to start up correctly and give me the SWTBUG prompt. What I did was remove an overwrought modified RAM board and replaced it with a more basic 4K board set to the $A000 range. That worked great for a while, but not we're getting back to the situation where I power up many times and get either ? marks, a string of 4s, or some other random character. I have to power off and on several times before I get the $ prompt. I figured out how to run a proper RAM diagnostic and no errors came back. I wasn't sure how to properly test the $A000 board - I assumed I couldn't let the test test the address space used by the test program itself, so I set it to run from A07F to AFFF (I think I did that right, I set the MSB in A002 to A0 and LSB in A003 to 7F, and for the upper limit MSB in A004 to AF and A005 to FF). I'm wondering now if this is really a RAM problem or maybe something else. I don't think it's the serial card.. I've tried both the MP-C and MP-S and no change. I have an NOS MP-B2 motherboard here. The 'check pins' on the molex connectors for the cards haven't even been cut. I could set that up for testing although, being totally unused I'm hesitant about altering it. What do you think on that? Brad