AVR-Chat

>  Indeed.  The oscillator can be affected by the dynamics of the moment in
> your circuit.  Motor noise, ground bounce, power brownout, static zap
> and other even less understood issues.  Bomb-proofing your design is a
> major part of the voodoo we (hopefully) get paid the big bucks to do.

Exactly!

"works" for a hobby project is very different from "works" for a
production run of 1,000,000 devices.