spirits are completely recyclable, very exploitable bug

While playing the new 'Heart of gold campaign', I noticed that I could reuse spirits in the spirit chamber indefinitely: so basically in ever level I had 1-2 high leveled spirits and I could make my whole army level 10 in a matter of minutes. I would drop the spirit on the the unit standing on the pedestal and it would give the usual effect: leveling up the unit and if it reaches 10 it goes off the pedestal. But the spirit would not disappear and instead just stayed next to the pedestal. I could repeat this as much as I wanted.