Flyingbug,
I'm an Engineer by trade and when you see a number of catastrophic failures you check things out pretty carefully!
When you subsequently see problems with additional items out in the field alarm bells start to ring as it's apparent there is some kind of problem!
You can't seriously be telling me that this is all coincidence, surely??
Even if the fault is down to maintenance being carried out correctly (or incorrect assembly), it's still a design issue! Either your documentation is inadequate or the thing you designed is inherently difficult to maintain. Either way the designer is ultimately at fault.