What triggers enemies double or triple special moves on Marvel Contest of the Champions?

Sometimes enemies (NPC) have a full special bar, 3 full bars ready to go. But instead of using them all at once, they attack using a double special move and keep one as reserve.

What determines if enemies special attacks will be double or triple? and most important, is there a way to avoid them?

Solution 1:

The computer AI will not use a Level 3 ability in any quests. They can only use a Level 3 ability in an arena. (or during alliance quest)

[edit] since the writing of this answer, the Contest has evolved, and some quests have special nodes which allow a Level 3. Those cases are, however, quite clear as the nodes are very visible. As a general rule, it still stands that AI doesn't use Level 3 abilities during quests ... baring special nodes ;) [/edit]