That's good info from BD.
What I found when I was having similar issues, the plastic cable housing with the two "ears", at the trans bracket by the manual shift lever. This was not fully seated, the plastic housing snaps into a hole in the bracket, the two ears spread out to hold it in place. One of the ears had not expanded so the plastic bracket was not being held securely enough. I simply shoved it in tight, the ear expanded, and all has been good since.
In my case, the plastic housing had most likely not been seated properly by me. I had disconnected it while installing my TC/3-4 Lockup switches... .