"smartphone doesn't boot reliably when the ambient temperature is below 40 degrees fahrenheit" (temperature lowers the battery voltage + high power usage during startup = voltage drops below FCC-mandated minimums for the antennas -> automated SoC shutdown)
"bluetooth controllers won't pair reliably in building 17" (too much interference to pair if there are more than ~100 other bluetooth devices nearby)
The combinatorial explosion of external factors in this kind of bug is insane - you just won't have a good time without dedicated folks whose focus is chasing these down (and I'll take a good QA over a good engineer for this sort of investigation, any day).