Swedish Armed Forces Pack Issue

[Sully]

I have a friend connecting using the vanilla launcher to download the mods. They all check out and he can join the server most times. However, occasionally he gets kicked with an error message something related to "Swedish armed forces pack". I believe this mod is part of the OFPS Pack and he's already deleted and redownloaded that mod, but it's still happening. Sometimes right at the start, sometimes and hour into the gameplay. Any ideas? Thanks all.