Animation stops playing as soon as AnimationClip.AddEvent is used.

Hi there, I am adding an event to a looping animation on runtime via the following code.

 animclip.AddEvent (new AnimationEvent () {functionName = "TheFunction", time = playbackTime});

the problem is that it's stopping the animation, setting all mechanim booleans to false & transitioning back to idle.

I've set the animation in question to loop and be non interruptible.

Why would this line of code force a transition out the animation it adds an event to?

Thanks in advance for any help anyone can shine on this!