"Show party in raid" has been said not to behave with main tank frames
Well, then I missed when it have been said :)
Tried without MT's MTT's frames. Party shown ok but still got same error messages spam. Also with buff filtering enabled it shows oil buff on weapon on player frame in party ("Show Player in Party" option enabled).
Guess I need disable some frames to get "Show Player in Party" option working too ? :)