It's hard to figure out if a device will work to spec offline.

For instance, our home HVAC shipped with blatant firmware bugs that eat blower fans, lock up compressors, etc, but take a few years to do it and access to the hidden service menu to diagnose.

Eventually, I broke down and put it online to get the firmware update (after a $500-1000 fix "in warranty").

(It's a Bryant.)