Multiple Screenwide Animations?

[tangedlwebgames]

I'm having an issue with screenwide animations called from events. It seems to me that one screenwide animation will cancel another if they begin on nearly the same frame. I've tested these scenarios:

• Both start on the same frame = only one shows
• One starts, then the other starts 1 frame later = only one shows
• One starts, then the other starts 2 frames later = both show

The animations are being called on separate parallel events, and they target the events themselves. What are the rules governing this? And is there a way I can prevent one screenwide animation from cancelling another?