Was playing a Normal Game After Wave 10 finished, I selected Sorcerer and proceeded to spawn a Disciple to use it on. Completely forgot to actually use the spell after selecting it and was greeted with the friendly Taxed Allowance and 90g. After Wave 11 ended, I selected my Disciple noticing the Buff Arrow to apply the Legion Spells. Selected Sorcerer since it was there and it worked like normal. I haven't tried to reproduce it but I would assume that the other Spells that are similar (buffing one unit) could also fall into this bug if they are coded similarly.