i have a noname car stereo which is looping up various tapes

the tape, instead of going nicely around the takeup reel will loop
around the supply reel.

i opened it up to see how it works

there is only 1 sprocket for play and fast forward.it doesnt have a
sprocket for reverse. i cant understand how the tape can loop unless
the motor somehow intermittantrly goes beserk and drives the tape in
reverse! any theories? thanks