I am not sure which version of Channels caused the issue but I have seen it consistently over the past couple of months. Here are a couple of scenarios with what has worked with HD Homerun / Channels app / ATV4k. All devices are hardwired.
Scenario 1 : ATV4k-> 1080p TV, no audio or video stuttering.
Scenario 2 : ATV4k-> 4k or 4k HDR TV, audio is ok but video is stuttering
Solving for Scenario 2 -
Within Channels app, go to Settings -> Transcode -> Set it to "Heavy".
Originally my Transcode setting was set to "none", I set it to Heavy. Stuttering is not totally gone but is significantly reduced.