C7500 keeps losing connectivity but comes back

I came from a C7000 and I was on xfinity.  I kept losing WiFi signal and had to keep rebooting my modem.  Called xfinity and they blamed my equipment without even checking my line.  I got a C7500 and speeds were quicker but still having the issue.  Xfinity came to house found FM interference on my line changed the wire but said everything looked fine.  Still happening.  RCN just came to my neighborhood and installed all brand new lines so went with them today and not happing as much so far but seems to be happing a bit again, and speeds seem to be inconsistent.