What I think is most interesting is that I can also hear the sound of (sounds like arcing) in the main transformer across the street when the machines break and to me that's crazy!
That arcing noise could be the hint. I've had a massive main transformer feeding a manufacturing plant lose a neutral connection internally. A lug had a loose bolt and created the problem. They said it was probably arcing and heating up for weeks, so we used an infrared camera to check all the other connections feeding the sub-panels. These was pretty big stuff with 600-amp 3-phase breakers feeding the sub-panels, and lots of damage happened from the open neutral.
It would be really interesting to have your journeyman electrician or power company pull the access panel from the big transformer and watch it at night while your machines break. However, be sure you use Arc Flash PPE gear (Personal Protective Equipment) since if a high current connection lets go while you're in blast zone, there will be an explosion of molten copper in a plasma hotter than the surface of the sun coming at you faster than the speed of sound. I've witness a few of those Arc Flash incidents, one up close and personal. And it's way more dangerous than simply being shocked.