Pioneer dc-z93 cassette issue

Hi all .. I have a pioneer stereo DC-Z93
as the cassette bands were broken, I replaced them, 
but now when I press play it will play for a couple of seconds one direction, 
then auto reverses to the other side for a couple of seconds , and just keeps going from 
side a to side b  each time after a couple of seconds, I even swapped the tape mechanisms over from 2nd hand unit, and still does the same..even when  FF or RWD it only goes for a few  seconds then stops..
Does anyone know how to correct this please… 
Thanking you..