727 B&M star shifter problems

It could just be a cable issue again. Since you said you already melted one it makes me think it's not routed properly. I might be wrong but my guess is you have headers which makes cable routing very difficult and that's the real issue. I put a B&M quicksilver in my Cuda and thought I had the cable routed good enough but in less than 10 miles it melted and froze up internally. I had to buy a 5' cable to route it better so it was clear of all header tubes. That was 3 yrs. ago and havent' had a problem since.