After a lot of tinkering and some replacement parts, the PDP-11/23 seems to finally be running reliably!
The current configuration includes the 11/23 CPU, 64K of memory, and the serial interface. I also have my two RLV11 boards for running the RL02 drive installed, but those are not yet working.
I did have some bad memory boards, but I also didn't know that the CPU test required more than 32K of memory. So I did have everything working at one point, but the test wouldn't even start. With 64K of known good memory, it runs and passes!
My next step is getting the RL02 drive running, which may be very difficult if the complicated drive mechanism needs work.
Here it is running the CPU test: