I have a similar problem which this guy encountered.
http://mudfish.net/forums/6/topics/19022
I can play black desert jp with full vpn mode perfectly but cannot do so with only the item equipped. I have tried other methods such as using other free vpn, like Softether, and chrome extension to launch the game, but both failed. Former would dc after I switched the connection from Softether to mudfish when I had entered the channel selection page; Latter even wasn’t able to trigger the launcher.
Hopefully I can use the item-only mode so I have a better network speed to watch twitch when using mudfish.