You are exactly right - that is how my cable failed. The arc swing of the lever wears an oval hole in the end, and eventually the thin plastic sheath inside to allow the steel cable to slide in the steel conduit can begin to poke out the end. I guess the ovalized wear acts as a slight funnel, so the plastic sheath pokes out, but then jams going back in, causing the cable to hang up. It'd be nice if the plastic sheath were glued in, so it could not migrate.
My other thought is if the plate where the cable terminates allowed the flexible conduit to pivot ... or just buy a new cable every 30,000 miles.
Yep . . sounds familiar.
I had a replacement cable made locally here in Oz - cheap, too.
On this cable, the ferrule fitting on the outer sheath that goes into the engine mount was metal, not plastic.
The metal ferrule also has slots much like a handbrake cable which allows fitment of a retaining clip.
I later made a new engine mount with the ability to use a retaining clip which positively ensures the outer cable won't jump out. I'd had the cable jump out of the hole on a couple of occasions on track days.
This new engine mount also has the hole about an inch lower which kinda sorts out the non-straight pull issue. It might be possible to achieve the same thing with the stock engine mount by adding / welding on an additional tang of some sort.
Remember too that the engine mount is rather prone to cracking/breaking in this area partly because of that big hole needed for the gear change mech.
I suspect searching for a handbrake cable may bear more fruit than for a long clutch cable if you're looking for the outer sheath as well. I wouldn't be surprised to find that's what the original cable was - a handbrake cable.
Essentially, it needs to be roughly the right length with a swaged threaded fitting on one end. Be prepared to figure out the other end & the possible need to shorten it.
