Decks, Patios, Porches and Docks - Fix for Wobble?

Can anyone recommend a good fix for wobble towards the outside edge of my deck?

I have a 15'x24' deck 9.5' high with 2x6 decking, 2x12 joists 24"O.C., 2x2x12 beam 13' out on 4 6x6 posts notched on one side. When anyone heavier than about 50 pounds is walking out near the beam, the deck starts to shimmy a little bit. This was not noticeable right after I finished, but has become more apparent as the wood has dried out.

The plans I used didn't have any allowance for diagonal bracing from the posts to the beam, (of course, they also called for 4x4 posts, which the inspectors required to be replaced with 6x6s) which I believe is probably a major part of the problem. I did try putting in a notched 4x4 in each of the interior corners between the posts and beams, but that didn't seem to make any difference. (I attached them with 3" deck screws however, so I don't know if that would be a substantial enough connection).

Anyone have some advice? It would be greatly appreciated.

Thanks

Of all of the dimensions you told us, I looked at just ONE -- the 9.5 feet high.

You need to crossbrace your posts!! And do more than what they may be now!

I've built decks 14' high, and "wobble" has never been an issue!