I can't seem to find any other mention of this, but there seems to be a problem with monstrology minions vanishing as soon as you cast them,
the spell casts, the swirl in the middle happens, then for a split second you can see the minions model, but then poof, TC consumed, no minion, its pretty frustrating, I just had it happen 4 times in a row
Fractel Treeminder is the primary minion this is happening, there is 3 other open, usually round 2 of the battle, had it happen in many different worlds and locations