Hey everyone, just wanted to share my experience with this issue, as I currently found a simple and supposedly bit perfect way to solve it.
My LG C4 was showing this exact problem (small intermittent audio dropouts) when using the optical out to send my apple tv's signal to a schiit modius e dac (ess chip). Having the tv's optical out first go through a fiio br13, and then sending the fiio's coaxial out to the dac solved the issue 100%.
Still not sure if it was excessive jitter or clock issues, either way my fiio br13 managed to "clean" up the digital signal before sending it to the dac for analog conversion (when hooked up this way the signal supposedly never touches the fiio's own dac, which might even be transparent enough anyway, haven't tested it). It also added a respectable bluetooth receiver to my system, so all in all I think it's a better solution than using HDMI extractors (which may or may not mess with the video signal going into the tv) or messing with the tv's arc output (which might output the same poor digital signal).
