Animation transition event firing late?

I am using a transition event to change the Y scale between -1 and 1 after playing an animation that chances the character from facing the right side to the left side.

It seems the event is firing a frame or two late as I can see the end of the transition occur before the scale is changed:
https://vid.me/MI4p
(note: frame rate prevents you from seeing the model before the change in scale is applied, I can assure you that it does actually flip between the two poses)

I have the transition duration set to 0s as it makes it even more noticeable if its a non zero value.

140085-ue4editor_2017-06-02_02-57-27.png

What can I do to get around this? Is the alternative to go through all the animations and redo them for the opposite stance?