Ah ha!! So that explains MY problems.
I just finished restoring my '83/84 Trek 770 that has a Cinelli 1R stem as standard equipment. I have several other bikes with the Cinelli 1A stem and never had any problems with the bars rotating. But with the 1R stem, I found the bars had shifted on the first ride. I tightened them up to what I thought was an adequate torque. Next ride same thing, bars rotated.
After the third incident, I threw caution to the wind and wrenched the handlebar clamp down to an inch of its life. All the postings regarding the 1R stem have validated my personal experience and have convinced me that I'm not going crazy yet.
Bill Silverman
Pasadena, CA, USA