Open neutrals are no joke but each case does give a good story every time again. I know a guy who cut a 70mm2 neutral in a factory. They had a lot of single phase drive inverters. I think somethink like 25 inverters had to be replaced (and a lot of other stuff too).

What do you mean by “galvanic isolator”? Link to coax example device? I’ve never heard the term before and a quick google is showing something irrelevant. NZer, so the language barrier exists!

Hadn't heard the term before. Looks like its two diodes in parallel, pointing opposite directions, in a very-expensive box. Blocks low-voltage DC flow while allowing higher-voltage AC currents to pass. Looks like maritime usage is common.

http://www.yandina.com/galvanicIsolator.htm

Probably an isolation transformer. A search for “cable tv isolation transformer” gives lots of results.

Wow what a mess