F150 transfer case

Not sure if I’m doing this right, I’m new here. But here goes!

I have a 2000 Ford F150 4x4 with a manual transfer case, Borg-Warner 4406. While driving down the road the t-case shifted itself into neutral. The shift handle didn’t move. It’s something internal. When I shifted into 4hi the case went to 4lo. When I went back to 2hi the case stayed in 4lo, but my front axle disengaged. So I got home in basicly “2lo” (front driveshaft getting power, but front axle disengauged). I got a used t-case from a junkyard, and was discussing the swap with a mechanic I work with and he said “You shoulda asked me before you bought one, I have one I would have given you. It just needs rebuilt. It shifted into neutral one day, and now is stuck in 4lo.”

is this a common problem? Should I start rebuilding my old one in preperation for when my “new” used one does the same thing?