eARC is capable of more bandwidth for lossless audio and I know has limitations at longer lengths for optical and active cables. Blu-ray is practically the only source that has lossless audio with few exceptions, so in theory if you aren't using Blu-ray, it shouldn't matter but this is HDMI. Definitely, try tuning off eARC.
Some devices with eARC can use ARC for audio but can turn off CEC. If that is available to you try turning off CEC. Before eARC regular ARC requires CEC to be on which can cause problems.