The tumble drier ( Creda ?) which we bought 25 years ago spun both ways, on the end of the drum was a screwed spindle, on this spindle was a nut that travelled in and out depending on the rotation, at either end of its travel it would operate a switch and reverse, but that was 25 years ago, its probably done with a computer chip now, if they still use the mechanical system it could be switching is stuck.
If it is spinning in one direction OK then the motor, the motor speed control, motor supply etc... are Ok and the fault must be with the main control module.