Replication of identical evidence over multiple diverse systems with and without any copper chemistry avoid any conflation.
THAT is how to resolve such issues! This is a legitimate concern, and the best way to address it is to use a different system.
I often say there are systematic errors in every kind of instrument. So the best way to prove a result is not caused by a systematic error is to use a different instrument based on a different system that cannot have the same systematic error. It will some other error, but that's okay, as long as they are in reasonable agreement. Long ago, there was a vigorous debate that went for weeks and weeks about whether a power supply might affect a thermistor. I said "I don't think so, but try a mercury thermometer instead." They said, "maybe the power supply will affect mercury." I said: "okay, turn off the power and see if the thermometer changes, or move the thermometer away from the power supply, or try a red-alcohol thermometer." As I recall, no one paid attention. The debate went on. I ducked out of it.