Sorry for my poor answer. It looks like your issue is even same with Full VPN mode enabled + WFP Item mode disabled…
For this case, it’s hard to say why this issue happens. I think How to check the basic functionality link worked fine on your environment. With this assumption, I don’t think there’s a thing missed because we can assume that all traffics went through the mudfish node.
Please try to test with mudfish nodes first though I’m not sure that it’ll work for you. If it’s still the same with other mudfish nodes, it could be more related to a conflict between mudfish and the game client.