It may simply be that the contacts are gummed up and need to be cleaned real good. When I've had to clean the samll contacts found in such devices, using a high quality denatured alcohol (Home Depot) with cotton swabs and/or a non-residue spary contact cleaner solves such issues. If the problem is in the cable itslef and if it's a RJ45 plug, you might be able to re-purpose a CAT 5 cable or terminate a new (what...an 8 conductor) coiled cable. Something like what you see here: http://www.kenselectronics.com/lists/micpart.htm#Cords
,but find out how many conductors are in the cable now. I've replaced two mic cables of late, one was a 2m rig and the other HF (refurbished a D104). If the electronics are what's failing, then see what Yaesu charges for the inside replaeement part.
Glen - KE7FD