Either your cables are made with the absolute worst insulation I have ever heard of, or your environment is doing something to the cable. I have done networking in 200 year old building with CAT3 from the 1990s that still works today. I installed a CAT6 cable in my parents house in 2003 that still works.

If I ever had a cable in a wall just go bad I would put that cable vendor on the blacklist immediately. Is it possible that the cables are being damaged during installation?

I agree that wifi is a great fallback option, but what happens when the cable running to the AP deteriorates?