Spark plug number eight problem

I have a friend who is a mechanic who works on my truck. About seven months ago he gave me a tune-up, replaced the eight spark plugs. In about maybe a week maybe two, number eight spark plug started to misfire (I hope that's what it is called). I got a diagnostic test and it was flagged, we assumed it was just bad from the get-go. It was okay for a while, then a few months later, same one number eight started up again, so my friend replaced it. That one lasted for not even a day, then pop, there it goes again, same old number eight.
It is just crazy, the same spark plug three times, it has got to be more than odd. I know this sounds crazy but I will mention it anyway,. My friend mentioned that it looked like something was trying to make a nest or something on it, I do not know if that is relevant or not, I live in Virginia and there are lots of critters so I did not pay a lot of attention to that, but he said it.
Also, sorry, also a check air suspension or air suspension off is coming on, one or the other, what does that mean?
Thanks so much.