The level one spell "Nahal's Reckless Dweomer" available to the 'Wild Mage' kit can be cast infinitely.
Also it cannot be correctly added to the quickspell bar: selecting this spell takes you to it's second menu where you select any spell from your spellbook and adds this to the quickspell slot.
Loading this save in a regular BG2 save also has the infinite cast issue. Quickspell functions correctly (add's Nahals... to the bar). Creating a new wild mage, the spell is expended on use like any other.
Ok, the problem was that Target type 7 shouldn't be cast when setting up the quick slot. This turned out to be a purely guiscript problem. If you don't have the git sources you can simply fix GuiCommonWindows.py
Add this: if Target == 5 or Target == 7:
instead of checking only target type 5.