High cast speed cause the first Volcano not to spawn when casted from a shapeshifted form

I'm not entirelysure it's caused solely from the cast speed, but it's the most probable explanation I have, as when I'm slowed the problem seem to disapear.

The animation is played, the mana is consumed, but no volcano appears. It makes playing volcano build kind of a pain, as I have to hold the spell to be sure it's placed properly from an animal form.