4. Samsung ML2950 paper jam

Samsung XPRESS SL/M/ML 2950/M2625/M2825/2675/2676/2875/2876/2626/2875 paper jam from 1 tray. Why? The problem also occurred after replacing the sheet pick-up roller. after that, only 1 thing remained to check the gears and stepping motors. I immediately replaced the 2 stepping motors due to lack of time, and then it was fine!