With your HDMI ARC connections, you are feeding the HDMI connection from the TiVo to the TV and then an HDMI ARC connection out of the TV to the soundbar or does it go to the soundbar first and then to the TV (sorry have not done too much with ARC and the manual for your soundbar wasn't too clear)?
Have you tried feeding the audio directly from the TiVo via digital audio cable to eliminate the new TV from the audio path?
Scott