OK, short version

Mopar elected to keep the same 'basic' valve body that has been used forever
in the 904/727 and added a piece on for OD and lock-up with the advent of
the 500/518 units

then they decided to stay with it when they went to the 'electronic
governor'

the vehicle speed sensor tells the ECM what the speed is; the ECM tells a
'governor pressure solenoid' to generate a hydraulic pressure corresponding
to vehicle speed

so far, so good, if they'd stopped there............

but then the 'diddle with it' urge overcame common sense, and they added a
'governor pressure transducer' to feed back the GPS pressure to the ECM, to
'see if it was working right'

unfortunately, the GPT doesn't read the pressure right (thinks its too low)
and the ECM tells the GPS to jack up the pressure

a scan tool will show 'governor pressure' of 20, 30, even 50 psi at stop,
when it should be zero

result is 2nd, 3rd, or even 4th gear starts

get a scanner on it and watch the 'gov press' line when it acts up

G