nsm 240 I

Hello I am new to the nsm world and I am having some issues with my 240I.when selecting a side b song the mech. will scan to the picked number, it will pick the record, clamp it in and then the turntable motor will stop. if I turn by hand it will play but not continue to run on its own. if I slide the tone arm to the end of the record it will cancel. side a works fine.
thanks for any help you can give me,
Paul