Wait, holding scissors wrong was messing up your whole cut? That blows my mind.

Birdbath trick worked for me too, way better than expected.

I read a NTSB report a while back about a chafed harness that rubbed through and caused a fuel gauge to go nuts mid-flight. Seems like the fix was the same thing your lead said, leave a little slack so the wires can move without grinding on each other. Tight looks nice on the card but the vibration always wins in the end.