What is the function of the TRAY plate on the conveyor belt in the solution with the error described as Rear section PLC2-M7130?

What is the error id of 291 in the solution with the error described as Rear section PLC2-M7
One possible solution for this error is to physically remove the TRAY plate from the conveyor belt before the PLC2-M7130 can be accessed. This should prevent any interference or damage to the belt caused by the plate's