I recently learned that is is possible to purify all the sprites in FSC without activating the well making it impossible to progress. If 4 sprites are already purified, 4 players need to be holding the other 4 sprites over the circle. When one is placed, the other sprites are forced to purify as well, but the game only notices that a 5th was purified and ignores the other 3.
I noticed this when I went to purify the 5th sprite and a teammate placed it before I could. 6 were in the circle, but the water didn't spawn. The next run, I tested my hypothesis by purifying 4 sprites, having 2 teammate stand on the circle holding sprites, and then purifying the 5th. As I predicted, the 7 sprites present purified, but the water didn't spawn. When we put down the 8th, the game recognized that there were enough sprites and we progressed, but it is safe to assume that if all 8 were present during the 5th sprite's purification, the game would have only recognized the 5th.
I noticed this a while ago, but never thought through the implications. Another reason to be lazy and use only one sprite.