[Tutorial] How to play multiplayer using Tunngle

[ShiNoMondai]

Can't quote, because "no clickable links are allowed", what the...?! Nvm.

We already have UPnP activated and I stated that all necessary ports are forwarded by UPnP. We even manually added them once, but it did not solve the problem!
We have the green smiley in the corner with a smooth 7-25ms latency on tunngle premium, this is not the cause!
The problem is we did everything what is written in the guides on the forum, even tried it without the build-in adhoc server and used the old exe, because we thought it was the cause of it, but nothing and switched back again.

We narrowed it down to the point that something wierd must be going on between my friend A and all other persons. It is only him that breaks off, doens't matter with who he plays or who is hosting. We are at the cross roads and can't seem to think of what causes the problem.
It is a really tough one.

EDIT:
If it helps. We used to play MHP3rd and MHFU about 2 years ago. My friend and I did not changed the system and did not re-installed any drivers or something like that. The firewall has every exception marked and should be let passing everything from ppsspp through, even deactivated on both sides it does not help. Simply we even used older emulator versions with settings set from scratch but no help at all.