Thanks Otto. Would a 6ft cable possibly solve the issue? That’s going to be a tight run, but I may be able to make it work.
Should I just run an optical cable instead? Would I lose anything if I just let HDMI do video and optical, audio like the old days?
6' is well within the certification range for passive cables (up to 25') but you do want to give yourself some slack at the source and sink end so you are not putting any undue stress on the HDMI input/output.
You need to be clear on what you mean by an optical cable. When I use the term optical cable I'm usually referring to toslink, which is an audio-only optical cable and has an optical connector, which is different from HDMI, USB, RCA, etc. There are fiber only cables but I don't know how wide-spread those are in use for consumer home theater systems. A hybrid fiber cable is what is best for long runs. A hybrid fiber cable is basically the best of both worlds, copper only and optical fiber. Those cables consist of glass fiber optical cores surrounded by solid copper wiring. They work extremely well for runs over about 20'. At 10' or less I'd try a Premium High Speed HDMI cable (certified) because they are a lot cheaper than hybrid fiber and are certified to meet all HDMI 2.0 option sets. Hybrid fiber cables are active, in that they draw some power from the source and sink end. Unfortunately, HDMI.org does not allow at this point in time for active cables, any kind, to be certified like they do for passive, copper-only cables. HDMI 2.0 is the current finalized specification so if HDMI 2.1 is something you're concerned with I wouldn't worry about that.
Keep in mind that the cable is just the data path. It just carries the signal from the source to the sink. It's the HDMI chipsets at either end of the chain that determine what you can see/hear, not the cable. Try a Certified Premium High Speed HDMI cable first, being mindful of bend radius and see how that works. If you still have issues, then you need to look at your hardware (any recent updates, are you using CEC, etc).