Reverted to the original firmware, and everything behaved normally.
Programmed to 650/620, and the strange behaviour returned (showing less than 45 chips per chain - not showing xxx's, but just showing fewer ooo's)
Programmed to 660/630 @ 550m, and it was wonky for the first power cycle (hundreds of HW errors), but after another power cycle it's running with zero errors (one error after another 10 minutes), about 2500 GH/s drawing 560 watts.
I guess that, for whatever reason, these boards won't tolerate the 650/620.
(I would post screenshots, but I'm assuming I don't have that feature until I'm out of "Newbie" status)
Can you revert to the original Bitmain setup? I'd try back there to see if it's related to your changes, or something else.