Before assuming the hand is faulty, try the following:
1. If it is a model without the expansion door, check where the audit is failing. If allways in the same place remove that cartridge. If the audit now passes then fix the barcode on that cartridge.
2. If failing in random places during audit then clean both sides of the plastic lens in front of the LED strip. Be careful, it is fragile.
3. If the above is no help then the camera has gone faulty. It is common only to find out during an IPL as the camera is switched off after an audit and not used in normal operation unless you enter carts via the CAP door. It the problem is a cartridge barcode and you remove it remember to do an inventory from the host.