I've got the original floppy controller board plus a Quadram Quadboard, VGA board, XT-IDE board and a 3Com NIC.
As a test, I assembled the source with "ENHANCED_KEYB = 1" commented out. That seems to have solved the lockup problem with Control-Alt-Delete (but since that problem was intermittent, I can't be sure. Maybe I just didn't test it enough times).
Now there is some sort of keyboard related problem. When the PC finishes booting, the PC is unresponsive to the keyboard. It kinda seems to me as if an Alt or Ctrl key is stuck on (somewhat like Windows "sticky keys"). Sometimes I can get the keyboard to work by punching keys until something shows up at the DOS prompt, although it doesn't always seem to be the same keys that
make it start working.