Polk Audio Signa S2 Ultra-Slim TV Sound Bar - Sound going tinny then normal

I bought a Polk Audio Signa S2 Ultra-Slim TV Sound Bar (AM6214-A) which I've been using without problem since May 2020. Recently the sound has started to have a problem where it will frequently get very tinny/hollow, like all of the bass cuts out, for just a few seconds, then it comes back to normal. Once you notice it, it makes it hard to enjoy whatever you're watching or listening to. It's connected via optical cable to a Roku Ultra, and I've tried a variety of different apps but it is across all of them: YouTube TV, Netflix, Amazon Prime, etc. The Roku doesn't have much by way of audio options. I've submitted a support ticket to try to help diagnose the problem but I figured it wouldn't hurt to see if anyone here had a similar experience.

Thanks much.