Cables have also been more or less ruled out as the issue for a number of reasons.

First, the problem only occurs on specific parts of specific software. A cable issue would most likely be continuous. I've tested about 20 or so titles on the Gamecube and about 10 on the Playstation and these were the only two that gave it problems and even then, there were particular parts that didn't have the problem.

Second, removing the Playstation cable from the 1070 and connecting it directly to the TV's inputs removed the problem. Going back to the 1070 the problem resumed.

Third, the chances of identical failure on two completely different cables seems very unlikely to me. I have two sets of cable for the Gamecube (since Nintendo uses the same format for SNES and Gamecube) and while the problem alleviated when I switched cables and plugged it directly into the TV, when I then used that same cable and plugged it into the 1070 to confirm that the problem still existed, it still did even with a different cable.