I have had the PRL since Dec 2002. The elevation system has operated smoothly, if a little snug, until recently. Saturday it got to the point that I had to use quite a bit of force to turn the handle. I removed the PRL from the table and loosened the chain adjuster to determine what part was binding. I found the drive sprocket to be the culprit. It was tight where it protruded through the surface plate. I disassembled the sprocket attaching hardware, making sure the chain and other sprocket did not move. I had to use a socket wrench and mallet to get the sprocket out of the plate. I put the sprocket on a 3/8" tee handle hex wrench and chucked it in my drill press. I used a piece of emory cloth and a block of wood to sand the journal so it slides in the plate with no resistance. I only had to sand about 2 or 3 thousandths off of it.
I think the sprocket was a little snug to start with and operating it over time may have produced enough heat to expand it. It works even easier and smoother now than when it was new.
Incidentally, I found that using a speed handle and 3/8" hex socket wrench works better that the crank supplied with the PRL.