[cududa]

But why not have more buffer in their supply chain so that when someone notices missing bolts, or bolts need to be replaced, they have them?

There are clearly deep quality problems that have gone on beyond the door plug. Something is just off in the culture that it's completely normal to just have a lot of bolts missing, because it's within tolerance. If bolts come loose in non-visible places, that's what inspections are for.

The culture is apparently "eh there's missing bolts and it's too big of a pain to schedule and order them" for something that, in this plane's case, took minutes to fix.

That's a symptom of a very broken culture

[s1artibartfast]

Where is this bit about the supply chain and missing bolts coming from, or the part where someone knew they were missing and ignored it? Was that in a different article?

I guess my main point is that it is very difficult for outside amateurs to judge quality culture. They dont know the risks, severities, and existing controls. Therefore they dont know if something is completely typical and acceptable, or outrageous.