The pivot screw on the knife is too loose.
Remove the pivot screw (Torx # 5 or 7, can't remember), clean the threads with alcohol, put a drop of blue Loctite on the threads, carefully screw the pivot screw back in.
Here's the tricky part - with the blade in the open position, depress / disengage the liner lock and reach UNDER the blade (from the spine side), pinch the blade, and wiggle in left and right. If there is any play at all, tighten the pivot screw about 10 degrees; repeat until there is NO side-to-side play with the liner lock disengaged at all.
Let the knife sit overnight for the Loctite to set.
That should take care of the problem. The down side is that when opening the blade, a very definitive flip of the wrist may be necessary.
Hope this helps!