Intermittent loss of IPv6 connection

Hello, I’m having some intermittent connectivity issues with the XB3 we’re using. Sometimes, a general failure of IPv6 availability occurs and usually a modem reboot fixes this for a while until I start dropping packets again, followed by another loss of IPv6 availability. I use a couple of apps that work better with that protocol and would like to see what my options are here. Just as a heads-up, the gateway is in pseudo-bridge mode, connected to a Netgear Nighthawk RAX20 on Firmware 1.0.2.82_2.0.52. IPv4 seems to be fine, not dropping any packets or seeing any real concern regarding loss of connectivity there.