According to LT1236 datasheet, NC pin is connected internally. Where NC pin is connected internally ? How much the resistance is between NC and GND ? The customer measured it. One is 1.82kohm another one is only 1.57ohm. What's happened the IC ?
As additional info, there is a capacitor between NC and GND on the pcb because they used MAX6250 on their old version pcb instead of LT1236. Does the capacitor cause any problem ?