Following this one.. I'm having the very similar issues with a 71 Duster.
Problems with adjusting park, working once then not working next cycle. wont start in P, just N
Also have noticed button not going far enough for 1st.( sometimes it does but the next time it wont)
Am going to check all these this week>>>>Sloppy shifter and possible length issue with the trans lever.
Car has been apart 30 years.
Thanks!!