PDP 11/40 Unibus termination query...

Hey all -- I'm one step closer to bringing my 11/40 back to life -- the front panel is now responding and I can examine and deposit memory. But the machine is only responsive without the Unibus terminator (an M9302) installed. If it's installed, the front panel is basically hung -- toggling "Start" causes a brief flurry of activity, but that's the only thing that causes any response. Without the terminator installed, the front panel more or less works, I can examine and deposit memory, load the address register, etc... but I can't get any toggled in code to run, obviously -- it traps to the bus error vector at 00004. (There's also an odd issue, which I doubt is related, but Examining/Depositing does not correctly increment the address -- starting from 0, it's "0, 2, 6, 12, 16, 22, 26..." and if I start at 1 it's "1, 3, 7, 13, 17, 23, 27...") I currently have the CPU boards + MMU option installed in the correct order with a SLU card in the SPC slot, and an M981 connecting to a 4-slot Unibus backplane with a single 64K MOS memory card (M7891) in slot 2 -- all other slots have grant continuity cards installed. The Unibus terminator is installed in the last slot. Any ideas? Thanks as always, Josh