Invisibility Spell doesn't work properly as intended

[Soelaire]

Describe the bug

As described, it was supposed to drain 15 mana in exchange for every 3 seconds of being invisible, however, it appears that a person only stay invisible for a brief (1-3 seconds) and it doesn't drain mana at all after casting it (it only takes 25 mana and that is it). Therefore, I believe there is an error that causes the spell not to take mana at all and take the caster out of its effect after a few seconds has passed.

Minecraft username:
SoelaireCS

[Benlier]

This appears to be an internal issue with MagicSpells
I'm trying to get support from their community