sharp mxm-m450n the paper stops at the last roller at the reverse unit

Hi!   the reverse unit of my Sharp mx-m450n doesn't exit the paper. it stop at the last roller of the reverse unit. When i check the step motor at the exit of the reverse unit whit the simulation, works very well, but when i make a copy dosn't work. All the sensors are ok (POD1, POD2 and POD3?.

Please help me.

thanks.