Bob DBF
Contributor
Yes, sounds like a plastic rot.
Plastic rot usually starts with a bad batch, or bad formula, of plastic. Exposure to sun (UV), excessive heat, ozone, extreme cold, will shorten the life of any plastic, but normal care will avoid these conditions and should easily last over 5 years.
I have a lot of old gear, several times that age that I use occasionally showing no issues. Some go back to the early '60's, I don't trust it nearly as much as my new gear, but it is still functional. I would bet they tried a new plastic, or the quality control was lacking.