The keyboard affecting your external vocal processor is strange. I was using my back up harmonizer, Roland VE20 recently and noticed that it was somehow adding reverb to my PSR S750 keyboard sound. That never happened before. I spent some time with the Roland back in September waiting for my main unit, a Digitech V3 to be repaired. Worked with it enough to be able to get by if my Digitech was not fixed on time. I certainly would have noticed anything weird at that time. It was only recently that I noticed it effecting my Concert Grand Piano sound. I find this very strange. Let us know if you find the cause. By the way I'm going through Bose too.

God Bless,
Don