I currently have the Couriers Calling quest from Maia, i want the assassinations to fail, so in Port Maje i didnt help find the stalker and just gave her the missive.

 

For Tikawara i didnt select Maia for my party but when i get near Harama her dialogue pops up anyway forcing me to intevene and help him ( i dont want to).

 

Is this a known bug or are you forced to help him?

That sounds like a bug. I've never seen the game do that.

 

However, you can let it happen even if she's there. But I think you might have to kind of be a **** about it.