There's not much you can tell from a photograph of limited resolution. Looking at what you've offered, you might re-examine locally:
I expect these are mostly reflections in the protective epoxy, or flow/tension marks formed in its application, but could be signs of contamination or damage.
Even checking point to point contact is a trial with this stuff.
Vibration produces intermittent faults on assemblies (where the parts don't actually shear off completely) The most suspect parts are those with mechanical attributes - the crystal as previously suggested, the connectors and bulky components. Reflowing the SJ of the latter might be informative - any uncharacteristic loosness in the soldered material of the melted joint is a giveaway.
As previous - an intermittent fault is unlikely to result in repeated DOA symptoms, but it can be recorded for posterity in the firmware, with DOA symptoms, or break small-signal paths with the same effect.
Did you try a reset on the 'dead' unit, before replacing it?
The fact that its replacement didn't involve the surrender of the defect unit (for a discount in pricing) is a signal from the mfr regarding their view on the viability of repair. They are in the most sensible position to do so, after-warranty.
RL