It seems as if your call to getMission updates the Text with the new value directly, but that could happen before the fade effect is complete. Instead, collaborate between the getMission function and an event listener on fadeOut that is listening for the effectEnd event to manage updating the text.
In the getMission function, if the effect has ended, update the text, otherwise, save the new text into a variable. In the event listener on the effect, if the new text has arrived, update the text, otherwise, update a variable to indicate that the effect has ended. You could also put this logic into one function that gets called from both getMission and the event listener.
