Would start with the audio connections at the tv and at Polk unit by inserting / unplugging and wiggling ends when connected and tv playing. (If you can make it do same errors, clean, lubricate connectors with Corrosion X or WD40 and repeat. Trying a new set of wires/connectors may do it.
If issues persist, check the various audio settings on tv as the dynamic sound options (theater, surround, etc.) can mess with a stereo input.
Relaxing is hard work
2005 25ft International CCD SS
2014 GMC Sierra Denali 1500 4X4 int. 3.43 Int sway/tow controller
1981 Honda Trail CT110 1X0..no sway control