I have talked with several ppl and......
This is for your Network Team, not dev......
Your VPN with twelv99.net may drop large packets because of DFBit and some devices in network has lower MTU than Server/twelve99 MTUs.
Try to do a Path MTU Discovery and ajust MTUs to the lowest.
We (Europe) should feel some diff.
Or you should use more VPNs and balance packet loads on them:))