I am having issues with finding the park and neutral position on gear shift lever

I took it to a garage, they changed out a transmission range switch, then they changed outa PCM computer and had to take it to the deler to have the serial number programmed. This did not get it working. I was told it was electrical issues, they got the van started and worked Ok for two days. The isue as rsurfaced and its intermittent, some times the van starts fine and the other times the gear shift lever wont select neutral or park and hence cannot get the machine started.