TC Helicon Play Acoustic... Demonic Possession or Psychotic Break?

New

I have one of the first TC Helicon Play Acoustic you could get in the USA. So new, in fact, they didn't even label the buttons correctly! That said, it hit the ground running with me and has made this working musician thousands of dollars. I've loved it's simplicity (I ditchted the mixing board for it!). I don't use nearly all the features. In fact, I only use it to route and sweeten me and my guitar. It has been a workhorse and has never let me down. Lately though, towards the end of the night, I swear it starts adding a bit of far off background vocals to the signal. At first, I thought it was patrons singing along, then I notice no one is singing. I've had a few folks ask me about it and frankly I am a bit puzzled. See, I don't use any of the harmony capabilities of this unit. Just straight up guitar, with some body rez and a little reverb on the voice. That is all. So... I wondered if anyone else has ever noticed any mysterious "voices" in the output of their Acoustic Play? It is very subtle. Just enough to make me question my sanity. Anyone?