Not getting 2Gig Speeds Anymore

To preface, my city first got Xfinity about a year ago and I subscribed to the 2Gig plan which worked flawlessly for the most part until recently. Now my speeds are only half that, consistently, and I don’t know why. I already chatted online, and a had a tech come out that said it was the city’s infrastructure. But I’m just confused why the speed changed when it was working fine for the past year. I read a few forums that mentioned that Xfinity might’ve loaded the wrong DOCSIS download life for my modem? For reference, I have the XB10. I’m just lost why all of a sudden the speeds dipped.