When you first capture a wonder, you will see a 20% "Wonder" bonus to public order. This degrades by 5% every turn until it's gone. This happens with all of the wonders. If you capture a new wonder, it will go back to 20% again, then degrade over the next 4 turns. R3dD0g, did you take another wonder in the meantime?

The Statue of Zeus wonder is currently bugged. It is supposed to give a permanent 20% bonus to public order, but it isn't doing that. It's only giving the temporary bonus. I've never noticed it's bonus reappear in any of my games, which is why I'm wondering if you had captured another wonder to trigger a new bonus.