I actually came up with a solution! Somehow it was missed by all the theologians over the years, but I'm quite sure it is a correct solution and out of the many solutions I've read, this is the only one that seems valid.

What if God is omnipotent, omniscient and perfectly good but just... isn't very smart? He's doing his best, okay?

You may wonder, if he's omnipotent, couldn't he increase his intelligence to solve this? Yes. Yes he could. If only he was smart enough to realise that =(