Well, I didn't get a chance to test a library, but I did find the problem(s)... Each 'wheel' had it's first LED (3 strings in parallel) on each of the 3 strings blown. They would not pass data.
Here is the weird part. on one 'hub' or wheel, it was visually obvious the IC was blown (tiny as it is), BUT the other 3 on the other wheel (also first in strip on all 3) showed no visible sign of damage-but were.
These were no doubt APA102Cs (or equiv). What we did was cut out these 6 LEDs, resolder wires connecting them in parallel, and made each 12 LEDs long. I ordered a few meters of replacements for stock, and when they come in from Digikey we'll take the customer unit back in and add the LED to the end.
Thanks everybody! I learned a lot.