I can vouch for this method also. I started getting “Power calibration error” and “Focus or tracking error” with my 716A. I tried the “disconnect laser unit cable” method, carefully vacuuming the unit, cleaning the rails and clearing the autostrategy database, and updating fw. One or more of these steps appeared to cure it for a while.
But then I started getting the same errors again and finally it refused to burn anything at all. Since I too was out of warranty I figured I had nothing to lose.
The lens didn’t actually look dirty but after swiping it once with a clean piece of fabric soaked in isopropyl alcohol it’s working like new. After having done the cleaning a couple of weeks ago I’ve performed about 20 burns of which none have failed.