**Disclaimer – This is purely speculation. Seems to have solved my problem.
I’ve had this issue on a recent project. I think this is a latency issue. The Facebook SDK requires that <div id="fb-root"></div> be on the page. This should be the first thing after the opening body tag. After this, you may see your initialization code.
For me, this issue was not consistent. I would occasionally see the bug and sometimes I would not. Thus, my conclusion of it being a latency problem. If the SDK cannot find the fb-root, then it must create one. Herein, is where I believe the latency issue exists.
Try adding this just after your opening body tag, but before your FB.init({});.
<div id="fb-root"></div>
This seems to have solved the issue for me and will hopefully help others as well. The v1.0 documentation discusses the reason for fb-root, but the v2.0 docs make no mention of the item, likely because the init script will add it for you if it does not find it.