Are you saying they are set to WiFi, so not connecting? Or are you saying they are actually connected to WiFi?
If the latter: How can the components be on WiFi, if they were never setup on WiFi? Answer: They can't.

If you didn't do it, that means 100% someone else is screwing with the system. Even if the customer is 100% sure they didn't do it, that just means someone came into the house when they weren't there and did it.

Unless you think the Sony components have become self aware and they guessed the SSID & password for the WiFi, then connected itself.