tool drop

Have Toyoda FH550SX with 200 tool magazine. 1 tool drops out of swing arm when doing tool change. It's a heavy kaiser bore bar and gets used on 3 different pallets. This is the weird thing tho...it is only dropping on 1 pallet and that is the only tool dropping. Already have checked and no damage on tool holder or swing arm. cleaned swing arm. What is causing this? The spring coil on both sides of the swing arm I can push in with no problem, but, if it is because of that why only 1 tool on 1 pallet?