I used to work in embroidery and the annoying thing about that is someone manning the machine would have known about the bunched up thread. It stops the machine, so you have to go untangle and rethread it to get it restarted. Proper practice is to then pick out the bunched thread and see if you can get it restarted in the same position, if not you bin the garment. Looks like whoever done that had at least three stops where they’ve just continued until it sorted itself. I was doing schools uniforms and would have been on the shit jobs for at least a week if something came back like that, you can’t pass that off as ‘I never noticed’.