Auto Gearbox won't change,broken govenor

[Bullifamilie]

on-going issues with my 1989 Auto Caravelle.

Currently will only drive in 1st and reverse. Drained sump and found the following.





So can this bit be put back? or do I need a new bit or do I have to buy a complete govenor? How is this bit held in place and what causes it to break off.

Never been inside and autobox, would be good to understand how the govenor works.

Any help appreciated