C6250 strange VPN problem

I'm at my wits end here with this issue - I work from home and connect to my company's network using a VPN (Cisco AnyConnect). I have Xfinity internet and my own  C6250 modem/router combo. I can connect to the VPN just fine using wifi, and speed tests show that my connection is more than adequate (usually around 60 down/12 up) most of the time when I'm working. However, about 5-15 times a day the VPN will disconnect and reconnect in rapid succession like 20 times in a row, kicking me off of Skype meetings and presentations. it usually takes 5 minutes or so to get a solid connection again, and there doesn't seem to be any rhyme or reason to when these drops will happen. From Googling a bunch, it seems to be an IPv6 issue although I know nothing about networks or IT so I could be very wrong.

I've tried so many things to troubleshoot this issue with no resolution yet. Company IT told me to talk to Comcast, Comcast told me it was Netgear's fault, Netgear told me there was no way it was their hardware and that I had no idea what I was talking about. When I'm not using the VPN the connection works fine and I'm able to do voice or video calls with no issue. Switching channels did nothing, neither does rebooting the modem. Before a recent move I had FIOS at home, and the VPN and Fios connection played nice with no drops or interruptions. This is making it seriously hard to do my job, and because of the placement of my router (in a roommate's room), always using ethernet isn't really an option for me.

Has anyone experienced this issue before? Is it a problem with my specific hardware or my connection? Am I going to have to just buy a new router and start over?