I have been experiencing this issue for some time, but now it's reached breaking point. I am being disconnected when finishing story missions or during cutscenes. I have been told this is due to packet loss and even the smallest loss means the servers DC you. I've searched the GW2 forums and done everything I possibly can from opening ports, disabling firewalls, repairing the installation, factory resetting the modem and much more.
I'm on a wired 200mb connection with a Hub 3.0 [VMDG505 / TG2492LG-VM]
I have been told a VPN fixed this, but I'm already paying over £40 for my internet and adding additional costs from third parties feels like something I shouldn't have to do.
As a fellow GW2 player i feel your pain, this has been a problem for years now.
Unfortunately a VPN is not a 100% guaranteed solution as i have seen the problem even when using a VPN.
Personally i have switched to using my own router and having the VM hub switched to Modem mode. This appears to have worked for me, i am not sure the reason why, but one thing i have noticed is that you get a different IP when in modem mode, so it could be routing through a more stable part of the VM network or it could be that the VM hubs themselves are the problem. I have a hub 2ac, so its not just the hub 3.
I will watch this thread with interest as it would be nice to see someone get to the bottom of this issue.