[CamperBob2]

Mechanical devices don't repair themselves.

Only because we haven't bothered building any that do. A cynical take would be that it would be bad for the economy.

[dwaltrip]

We don’t yet know how to build self-repairing machines. That’s basically the same as creating new life forms.

[CamperBob2]

Well, creating life forms would require us to create self-reproducing machines, which doesn't seem like the same thing.

This will end up in a goalpost-shifting debate where the extent of self-repair capabilities necessary to qualify as "self-repairing" is argued. I'd say that a fault-tolerant system is at least 50% of the way there.