So that's why a 2 systems were getting crappy speeds. Yes, 2. It had been used only to split a single drop from another switch between two systems.
New drop, happy clients.
Some stuff here is museum material.
When you tug the unusually weighted cable and you hear metal scraping in the wall 10 metres away 😬
Hope it wasn't too much of an arse to fish out. Or did you let sleeping switches lie? :)