I carefully pried off the back and was OK. (Mine didn't have much glue plus I saw the other warnings.) The problem was that right-click (left as viewed from the back) clicked strong, right-click was weak. I ended up tightening the adjustment screw all the way.
Then I cleaned off the rubber pads on the back of the feet, shot canned air where it seemed like crud might lurk, squirted contact cleaner where it seemed right, and carefully ran the corner of a sheet of typing paper under the metal plate that appears to get distorted and snap back to produce the "click." Then I put the back, back on.
Right now everything works great.