If you mean they drop straight away on resetting there are a couple of things.  If it happens EVERY time, the drop down coil could be locked on.  Reset the bank without the power on by hand and then turn the game on - if a target drops the coil is locked on.  Also, the lip on the target can get worn and cause difficulty getting a good reset. A quick fix is to use a file to get a sharp edge, of course the target will sit slightly lower, but this is usually too little to notice.  Other things that give poor hold are if the spring is pulling in the wrong way (try taking it off the target and putting it on the other way, believe it or not sometimes this works!) or the finger the target sits on has been bent by someone to an angle that does not work (compare it withe ones that work in the bank)  Finally, there is some adjustment in the 'lifting' along the bank through the allen screws that hold the arms onto the rod.  You need to adjust it so the end furtherest away from the solenoid is SLIGHTLY higher.  This allows for the torque and slop and should ensure all the targets are raised high enough to reset.

I strongly suggest the full rebuild - follow Nino's guide as these banks cop a hammering so a bit of TLC goes a long way

cheers
Ian