So you now have some "repro" situations and some "non repro" situations.

Is uptime a variable in any of them?

In other words, in the "non repro" situation, when you booted it into the BIOS, and things worked, it has obviously been at least restarted, but was it cold? And when you took it into the computer store, it had definitely been cold because you would have had to power it off and haul it to the store.