Brifter loose even with bolt tight How to clamp a brifter to the bar more securely if the clamp is already very tight?

More detail: After a small crash (no scratches on me, just a few on the bike), one Shimano Ultegra brifter was wobbling relative to the handlebar. I tightened the clamp bolt that attaches the brifter to the bar as much as I could, but the brifter was still wobbling. I undid the clamp, removing the brifter from the bar and saw that the clamp is a bit rusty, but looks intact. Retightened the clamp bolt as much as I could (the hex key broke), but the brifter is still wobbling on the bar. Before the crash, neither brifter wobbled. 

There is no bar tape or anything stuck under the clamp or brifter edge, I checked before retightening.

The Shimano dealer manual does not give additional info besides tightening the clamp bolt (http://si.shimano.com/pdfs/dm/DM-ST0002-05-ENG.pdf).
First thing to do is loosen the bolt all the way and grease the threads. If possible, snake a lube dripper in and get a drop of lube under the bolt shoulder too. That may completely fix it, but while you have the lever separate from the clamp, look everywhere you can see for cracks in the lever body that might be preventing the clamp from snugging everything up properly. Pull back the hood as needed to inspect. If none of that leads to an answer, next thing to do would be get better eyes on the section of bar it's trying to clamp, and also the clamp itself.

Given this started with a crash I'd be pretty worried that the lever body is broken somewhere.