Nighthawk XR500 with Verizon Fios dropping connection entirely every 15 minutes

[moopoints]

Just moved into a new place and had Verizon Fios installed yesterday. Am using the Nighthawk XR500 as the main router connected via ethernet to the Fios modem. Initially all was fine and I had a stable connection. Then since about 8 hours in, I am now consistently experiencing entire connection drops. I restart both modem and router and will have a connection for about 15 minutes until it drops again (Internet light on the router is red, router dashboard shows WAN IP is assigned but disconnected). 

What's the best way to identify whether this is a Verizon or Netgear problem? Are there any obvious settings I have not applied that would be required to make the router work with Fios? 

Much appreciated!

[FURRYe38]

Was the XR power cycled or factory reset to see these would help after the new ISP was installed? 

What is the Mfr and model# of the ISP modem the NG router is connected too? 

Modem Combo Units to be aware of:
Couple of options,
1. Configure the modem for transparent bridge mode. Then use the NG router in router mode. You'll need to contact the ISP for help and information in regards to the modem being bridged correctly.
2. If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ for the IP address the NG router gets from the modem.

[moopoints]

Thanks for the tips. I believe the modem is set to bridge mode as the Verizon technician knew that I'll be using my own router when he did the installation yesterday. I will check with Verizon support later to confirm.