Town and Country blows fuse in reverse

My 99 Town and Country blows the backup light fuse when put in reverse
or when driving on the highway for an extended time. The reverse fault
is constant in reverse and stays during the highway driving until the
car is stopped and put in park. This clears the problem for another
hour or two. Because of this, I don't think it is the backup lamp
circuit. The same fuse powers the ABS controller, turn signals, and
front air conditioner fan. I rigged a circuit breaker until I can solve
this problem.

I assumed it was the switch in the transmission but since it is inside
the tranny behind the valve body, I paid a transmission shop $200+ to
replace it without any resolution. They called the part a Prindle
switch and it appears to signal all gear positions through a group of 4
spring loaded contacts. Since this was not a complete switch, I asked
the shop for the moving part of the switch and was told that was all
there was. The tech said the moving part was all steel, not an
insulated set of contactors I would have expected. I did not see it so
I cannot be sure of his response.

Thanks for any help.