Xfinity internet spotty throughout apartment

We've had Xfinity internet for a while now and use the eero mesh system with it. About a year ago there was a power outage and when the Xfinity provider came to fix our network, he provided us a new router. Since then, internet in parts of our apartment is very spotty going in and out, even with the eeros. This is an issue we didn't have prior to the outage with the old router. Can you help with some ways to try to fix this?