By any chance have you had a hard time getting into park after such episodes.
The governor has a piston that pops at 10kph. After it moves the governor pressure builds. Once this has taken place it makes enough pressure to keep a reverse interlock engaged (prevents accidental shifting into reverse above 10kph). IT ALSO keeps the trans from going back into first gear as all 83 300Ds would normally. If this governor piston sticks the car won't go back into first gear or park as the shifter would have to move through reverse.
I've seen this happen on at least two 722.3 transmissions including the one in my 84 928 Porsche.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician