@thegibson Early in my career, I worked on a DIY warehouse management system.

The main item barcode scanning UI had bugs that, when scanning too fast the scans wouldn't register in the db.

I failed to do adequate onsite testing to uncover the bugs until several months after go-live. At the end, the bugs were fixed but for months the warehouse team had to deal with the chaos to find the many "lost" items and reconcile the picks.