XR4500 Slow down at router

Hello. I'm having a issue with my internet speeds. I have had this set up for over 1 year things have been great. All the sudden my speeds dropped from 300Mbps down to 158Mbps with upload speeds of 13Mbps now at 4Mbps. While playing games things have become super laggy and unplayable. Speed test on show 10 ping but when in game it's showing around the 40-60 mark. Everything is hardwired in. When I switch the connection from the XR450 straight to the CM1000 the issue resolved its self. I reset all the settings in the XR450 back to factory and redid the setup wizard. Router is up todate on software updates. What am I missing here? Any help would be appreciated

Thanks.