I’m no expert, but I’ll give you my two cents. I play bass guitar and there are two types of connectors between amplifier and speaker cabinet. First one is plain barrel jack, second one is Neutrik. I’ve been talking with local amp maker and he said something like this: "jack is fine with low wattage, but with more power you’d do better with neutrik - it has much larger contact area " So I believe this is similar problem. We were speaking like 400-600W of power where jack starts to be worse. How about vacuum cleaner or kettle? Or similar appliance that can do 2kW… Small contact and higher drain means more heat generated in that spot.