You might try setting the 4K box to 720p so see if the signal improves. The 4K setting is for viewing what might be availible over IPV (broadband Internet).
I am not a Comcast Employee. I am a Customer Expert volunteering my time to help other customers here in the Forums. We ask that you post publicly so people with similar questions may benefit from the conversation. Was your question answered? Mark the post as Best Answer!