If it is actually metal, a close inspection of the knife, plate, auger and housing should give clues on where it is coming from. Look at the friction points where surfaces make contact for signs of metal loss and wear. Don’t forget to check that back end of the auger where it enters the motor drive. There should be a plastic or brass bushing or washer there.
As mdseaside mentioned, you should be oiling the plate and knife with food grade oil. This is so when you start the grind they have some lubrication till the meat makes it through the auger and can act as a lubricant for the knife and auger.
Can I substitute super bind and sodium erythorbate for the carrot fiber and encapsulated citric acid
lesgary absolutely you can but carrot fiber is more aimed at a fresh product and since you are using sodium erythorbate I assume you’re making a cured product? You’ll be fine with the carrot fiber but in the future use sure gel for a cured binder