Well, it's the tension from the retaining ring's o.d. and the bezel's i.d. that provides the tension to hold everything together- The washer acts like a spring to provide resistance to keep the bezel from moving too easily- To turn the bezel, one must theoretically press the bezel to the case to flatten the washer to eliminate the tension in order to turn the bezel...
Everything prior to disassembly fit fine? Nice and tight?
...Only thing I can think of is that perhaps in the process of removing the bezel, the bezel got bent slightly out of round. If you place the bezel on a flat tabletop, do you notice any high spots where the base of the bezel looks like it might not be level?