My stereo paired Play 5s (supplemented by a Sub) have synced perfectly for years but in recent weeks have begun to "echo" with one speaker notably after the other by about 0.5 second. I de-linked them and re-paired them after updating to the latest Sonos software, which seemed to help, but after one day they were echoing again. Neither speaker (nor the sub) is connected to ethernet. I do have a Google Mesh WiFi set up, with this pair placed roughly between two units. Could that be the cause?