The 1R stem was a wedge piece that has cuneiform ridges on the bar/wedge interface. These ridges indent ever so slightly into the bars when the wedge is tightened. When you loosen the wedge, the interface "lock" is interrupted and subsequent tightening never seems to work quite as well as the first time, perhaps because the ridges are not quite as "sharp" or perhaps because the "dents" in the bars no longer line up perfectly with the "ridges" of the wedge. I am convinced this is the main reason why the 1R stem has so many detractors and people claiming they don't clamp down well.