Have 2 mzc 66 units about 5 years old and within the last year the keypads seem to be failing and causing poping and hissing in the speakers. I've read similar issues described as amp issues but i've replaced 2 keypads and it fixes the issue but at 120$ a keypad if the unit itself is killing the keypads i don't want to keep throwing keypads at them. Has anyone else had similar issues and how did you resolve or welcome suggestions. Down 5 of 12 rooms right now and debating how to move forward? Thank you.