Mine is perfect, and reliable. I use it with the AC adapter. Had a problem with it a couple weeks ago:
It started acting really weird. The readout was very inconsistent. Would turn off when I tried to put it into the checkweight mode. Then I remembered that I had put batteries in it when I first bought it. I looked, and they were corroded. Probably messed up the voltage level somehow. I cleaned out the battery compartment and put in new batteries. Worked perfectly right away. Now it's good for another seven years,