Gambler's fever dream seems to have prerolled the next spell it randomly chooses to prevent save scumming.
This is fine, the issue is that if it picks an invalid spell it will refund your mana while not rerolling, meaning it will always repick the same invalid spell over and over again. Leaving you unable to use it.
For example, if it picked stretch time and I have no buffs. I can click it again and again and it fails again and again. I need to toggle the switch to allow golden cookies, then get a buff or debuff, then use gambler's fever dream to bypass the block and continue using it.
I suggest that instead of a refund, if the spell chosen is invalid it will re-roll.