X-Rite 810 green channel problems

I have a Noritsu branded X-Rite 810 desitometer that I've used for about 10 years. Lately, the green channel has been flaky - when I go through the cal process, the green channel will read low, high or fluctuate quite a bit. I was curious if anyone had any insights into the problem, and if the fix might be easy. I know I could call X-Rite about a repair but I assume it would be alot cheaper to buy another one.