Tuner backlash is a very common problem indeed...
I have had peeps bring brand new top end Guitars in wondering why the buggers would not stay in tune... Guess what? Tuner backlash.....

In my experience, the only tuners I have come across that have been consistantly good are the Steinberger direct pull.. Their design makes it practically impossible for backlash to occour.

With the PBG supplied tuners, I have found some to be excellent and others average but on the whole for a budget priced tuner they are reasonable.