Oh sorry, i mis-interpreted the statement "handlebars are cock-eyed", it seems that your stem expander bolt and wedge are loosening.
Still, the same rules apply for the stem/wedge bolt, grease the threads and un-grease everything else, including the inset for the bolt, the inside of the stem for the steerer tube, and the outside of the stem for the steerer tube. You might also rough up the outside of the stem with some 40-grit or 80-grit stem, near the bottom, below the stem insertion line.
When I have problems with Cinelli bars, it's almost always a problem with the bars tilting up-down due to insufficient tightness near the pinch bolt holding the bars.
- Don Gillies
San Diego, CA