I once lost about a month to a USB issue reported in the field on some custom hardware. Spent several weeks failing to reproduce it (setting up multiple machine

I once lost about a month to a USB issue reported in the field on some custom hardware. Spent several weeks failing to reproduce it (setting up multiple machines to automatically hammer through typical usage). It eventually transpired that the issue correlated with cold temperatures and the recent outsourcing of assembly had resulted in some poor soldering.