Update on DAC module: found probable root cause from within my system setup.
Failure point on the module is the +5V input - only a few ohms vs GND. I found the +5Vdc supply transient of -4V relative to GND for 200µs. Most ICs don't do well with anything below -0.3V relative to GND.
(the transient is caused by design depending on a great deal of Grove wiring as a GND path, combined with relatively high voltage/current on other rails in the system. One solution is redesign for low-ohm, low impedance GNDs)
