Intermittent latency issues and packet loss Nighthawk X10 R9000

A couple things off what you said.

1. you said you put your modem in bridge mode. Makes it sound like a modem/router combo device. Not all isp's are that great with "bridged mode". You're relying on your isp's device to be functioning properly. its also why I asked what modem it is. What model is it?

2. The latest isn't going to be the latest forever. A number does help. As well as potentially a firmware update could be causing your issue. Expecially if you've had it >1 year and the problems only happened in the last month. 

3. Saying you've had xfinity out to test the lines doesn't mean a lot. There's crappy technicians out there as well as they only care about getting out of a house. I've had bad techs or one's who don't know whats going one. When you're having issues, you have to investigate every avenue. Not just "it isn't my lines because my ISP (who wants to function as cheap as possible) told me so". The screen snip of your connections page of your modem (upload/download signal strengths helps) and the logs help us to help you. 

4. "wired obviously". It isn't obvious. its why we ask. Not trying to be a **bleep** but things might see obvious to you but its better to put it in your statements because we don't know your layout or exactly whats going on. More details are better than less for troubleshooting.

5. What's changed in the last month? You've had it over a year according to your statement. What changed in the last month? modem? coax line? location of the modem/router?

7. You said what games and streaming its happening on. But is it all devices or just one? Again, wireless/wired and what devices. 

Something to try? From the sounds of it, you have a modem/router combo device based off your bridged mode statement. Turn the routing functions back on for the combo device, disable wifi on it, and place your router in AP mode. 

Another thing you could try would be to downgrade the firmware a version or 2. Maybe something changed that caused issue with your device.If you do this, make sure to do it over a hardwired connection and reset afterwards. manually reinstall it and don't use a backup configuration.