If my suspicion about the old housing is inaccurate, then it needs to be explained why the cable is tight along the whole length of the housing. Bear in mind the housing is about twenty months old because the bike was brand new when I bought it.

If CarQuest premium hi-temp disc brake & wheel bearing grease is garbage, then yes, I used "garbage grease." If that didn't cause an interaction with the liner, then something else must have. Like what? As I stated, everything was fine for three months before a problem began to arise. I think this is a learning situation valuable to all of us - "Don't grease brake or shifter cables unless the manufacturer says so."

Incidentally, the brake cables aren't greased, and they're fine.