Gotta make sure whoever installed it used expansion joints or slip clips, not fixed fasteners. If they screwed the panels tight into the purlins without allowing for movement, that noise is just gonna keep happening. I had a buddy in Calgary who fixed this by swapping out some of the fixed clips for slide clips, especially on the longer panels. Also check if they left enough room at the eave and ridge for the panels to grow and shrink. If everything's too tight, you're basically trapping the metal and it'll pop and ping till it finds a way to move. Thicker gauge metal helps too, 24 gauge is way quieter than the thin 26 or 28 stuff.

Ah man, that's the worst. I spent two days on one in my hallway last year. Pried up a whole section of plywood trying to find it. Turned out to be a loose nail right next to a joist. Just hammered it back down and the squeak was gone. Such a simple fix after all that work.

Oh man, "three radio swaps in the last year and nobody caught it" that is wild. I had basically the same thing happen with a Piper Archer I was helping a friend with. It had been through two shops for a persistent static on the intercom. I finally crawled under the panel and found the antenna coax was rubbing against a metal bracket, and the shielding had worn through. Taped it up and moved the cable, problem gone. I mean, it was just sitting there chafing for months, and nobody bothered to look.

Honestly I used to be all about the newer automated methods too. I thought why would anyone want to do things by hand when machines can do it faster? But then I actually watched a buddy run a manual ramming setup for a tricky bronze pour he was doing, and I totally get it now. The feel of the sand, knowing exactly when to back off or press harder, you just can't program that into a machine. Automation definitely has its place for high volume stuff, but for getting those fine details right, nothing beats a good pair of human hands on the job. It actually made me appreciate the trade more.

Honestly, @leoward has a point. It's like how people excuse a broken machine at a store or a delay on a bus - yeah it might be a one time thing, but it still makes you question the whole setup.