..... My brain hurts.....

So I'm at Fort Locke, and I'm trying to enchant the shield Georg gives us, but I keep failing. I'm trying to give it +2 enchantment, and the recipe book says I need a caster level of six. Now I've looked up information about the caster level mechanic, and I'm utterly confused on why it's not working when it clearly should.

Here's the thing. My KC is a Ranger 4, Wizard 1, and Paladin 1. Alright? So the Wikia says Rangers and Paladins count as half a caster level. So my caster level with this build should be 3.5 . However, I also have the Practiced Spellcaster feat for all three classes, and each copy of that feat increases the caster level for each class by four. So even if I were to assume that it adds only two for the Paladin and Ranger, since they count as half, that'd still make my caster level at 11.5 . And enchanting a piece of armour for +2 enchantment requires my caster level to be just 6. But every time I try to enchant the shield, I keep failing, with the game telling me my caster level isn't high enough.

The only way this can make any sense to me is if a spellcasting class with one level only can't count into the caster level, which would explain why I previously managed to enchant the shield when I reached the Flagon for the first time, by the time of which I've levelled up as a Wizard one more time. However, I didn't find anything about that on the Wikia. So that's my question. Is that the issue, or am I missing something else? And yes, all the materials are correct and I'm using the correct bench and spell.

...... So the caster level is only relevant for the one class.......... That's confusing...

Yeah, it's not explained good enough in the game, but the mechanics are the way they should be. The effect would be heavily overpowered if the feats stacked. People would take one level of other spellcasting classes just to boost their main class caster level. The price is too low for such a major enhancement.