coulda been moisture, ice, road crud, etc
certainly isn't the first mention of that issue, you'll find 3 or 4 mentions of it in the 4x4 section over the last 30 ish days or so
I believe one fella hosed his down real good, dried it off and it "magically" quit acting up
while that sensor can stick and malfunction, it's something you need to take a look at, if it's not malfunctioning entirely, it means that your linkage hasn't gone fully forward which can cause some abrupt actions of your t-case, increased wear, breakage, etc not to scare ya or anything, it just isn't something you want to entirely ignore
1200 bucks in a KJ is worth working out a couple bugs

Can't say i'd let it pass up if I had that opportunity.. not sure I'd care if it even had a drivetrain as long as the body / interior was in great shape