I have the same problem with a B&M cable operated shifter. The outer casing melted and the cable goes out the slot/hole when I try to move into any gear other than first. First gear is when the cable is stretched the most and the tension pulls it back into the cable housing. How it melted is a mystery ATM as I haven't figured out what heat source melted the casing. Usually the culprit is the header but the cable is a few inches away from the nearest header pipe.
