I can think of a few more things to check but other than this I'm stumped:
What did you lubricate the trem with? Could there be a sticky residue?
Is there any damage to the underside of locking nut clamps?
Is the new bridge an Edge? If so, which kind? There were some made with fat knife edges which were supposed to be more durable but don't always hold tune and need to be filed.
Is there any movement of the saddles?
Are the new posts Ibanez locking ones, and if so do they have a small ring cut into the post shaft below the pivot area? These are the current ones and have a larger pivot area than older ones allowing better stability.
Check the neck for movement and make sure the neck crews are tight enough; try pushing the trem all the way down, try and move the neck with your left hand (gently!) and listen for a 'crack' if the neck moves, pull the trem up and then push down again and try again.