I don’t have another HDMI cable that long, but your idea makes sense. I’ll get a second one and see if that helps.
The tv is mounted to our fireplace, so I don’t think anything happening on the floor would affect it. I have experimented with moving the laptop around, and with shaking it, but have not been able to reproduce the problem. If stepping on the floor is somehow moving the cable I would guess a new cable would fix that too.