I spent a bunch of range time with 2 Posi Lock equipped Burris's and found the same issue, once it locked they were fine but, if you unlocked and locked again POI would shift virtually every time.
I know going into it the the posi lock move the point of impact. I just like the security in knowing that once set the the POI will never drift. I like one of the previous posters idea about engaging the posilok for every shot when sighting in the rifle. That way once its dead on you won't have to worry aboutthe POI moving by engaging the posi lok.
-JR
