wild mage without variable casting level?

[Kneller]

Probably a long shot since the last post here was seven years ago, but I figured I'd give it a try anyway.

I'm running the GOG Baldur's Gate Complete version of classic (not EE). I have no other mods installed, just EasyTutu. I created a wild mage, and everything seems fine except the character doesn't seem to consistently have variable casting levels. More often than not, it doesn't work. I seems to work a little more often, but if I try to cast Improved chaos shield, it raises my caster level by 13 (far more than the +/-5). Any idea what could be causing this? Thanks!