James,

You made at least two more mistakes in your program. But they are principal.

You forgot the instructions JMP WAIT after the operator
STEER_R: CALL TURN_RIGHT
and after the operator
STEER_L: CALL TURN_LEFT

So you start to execute the interrupt routine. Your stack will soon overfill. Correct it like this:

....................
STEER_R: CALL TURN_RIGHT
JMP WAIT
STEER_L: CALL TURN_LEFT
JMP WAIT

By the way, I didn't use the emulators, simulators and translators at all. Only paper and pen.

Good luck,

George