@Jvck 

Welcome to the community!

If you haven't already, check to make sure your Deco firmware is fully up to date, as shown here.

Have you tried swapping one of the satellite nodes with the main Deco and seeing if the symptom persists? 

What does your network topology look like? Are there any loops in the network, potentially?

Have you tried contacting your ISP to have them perform a line diagnostic check to rule out service interruptions?

  @Jvck 

Thanks for the context!

Is your Xfinity gateway operating as a Router? Or has it been configured in modem-only, or bridge mode?

Also, is your Deco X55 operating in Router Mode, or Access Point Mode? Just wondering, since having both your Xfinity gateway and the Deco operating as routers may potentially lead to network anomalies as a result of a double NAT scenario.

Glad to hear you were able to get in touch with Xfinity, and they're working to investigate things on their end.

  @Jvck 

Thanks for the update! I'm glad to hear the issue appears to have been addressed with the replacement gateway.

As for your question - if the replacement gateway addressed the issue in this instance, then it is likely the root cause was either the gateway itself or something ISP-side. So, if a similar phenomenon happens again, I'd suggest contacting your ISP to perform any necessary diagnostics on their end to rule out their connection and/or equipment being the culprit.

If they do rule things out on their end, and the symptom(s) persist, then I'd contact our TP-Link Support Team using the phone, live chat, or email options here.

Alternatively, you can always reach out to our Community here on the Forum as well.