No one has said it yet, but the most common cause of a breaker being thrown is an overload or a short. It looks like you’ve determined it isn’t an overload since it happens when the device isn’t turned on. That indicates that you may have a short. The two likely places are the PSU (since it’s supposed to be turned off) and the cord (since the PSU wouldn’t matter). If the cord is replaceable, I’d try that first. After the cord I’d see about replacing the PSU. Hopefully it’s a standard part and not something you have to buy from Ender if they still carry it.