| We've sold a lot of AI amps and this is not something I can recall happening... fading out doesn't register. The Coda is warranted for five years, and you can certainly send an email or give Acoustic Image a call. They are very responsive, musicians themselves, and will gladly help you resolve any problems.
However, as you mention, it would be wise to track the occurence and keep a known good cable handy to use if it if this happens again, just to be certain that the cable or anything else in the signal chain is not at fault. The first thing I do when stuff gets whacky is hit all the connectors with contact cleaner, just to rule out any dicey connections. | 
