What if you “forget device” !? I’m having the same issue. Every morning I wake up and multiple new devices have logged in and I’m creeped out. We just moved. Is there a way to block this ahead of time!?!?!?
I have identified 33 devices in my xFi app(and website). Some of them are devices my extended family use when they come to visit. It took some work, but I was able to identify all the TV's, home devices, etc. by their MAC address and IP address.
Forgetting won't help. It will undo any pausing that you have done. There is no way to block ahead of time. There are a number of threads on that already.
An xfinity person may chime in on this thread and might be able to look at your specific issues.