best Ican tell, these shifters work where something glides across a circuit board as you move the shifter. there is lots of build up on the board and the contacts. I have seen posts where guys have opened the shifter and cleaned off this contacts area and solved their own problem,
Here is some data from the red site:
Why Shifter Lever Assy breaks on Jeeps
After several short term "limp modes' followed by famous 'circled" PRND on EVIC decided to check SLA module, also known as electronic shifter module (ESM), inside. Several people here claimed that after replacement of SLA module they got rid of the problem.
I started with some homework and found German (Mercedes) white papers about 722.6 gearbox. Documents stated that inside the module there are 12 Hall sensors to detect lever position. Hall sensors are known as pretty reliable ones cause they are contact-less sensors. Interestingly, I didn't found any claims on SLA module on several Benz sites.
However when I disassembled SLA module, I found that Chrysler put cheep mechanical contact system inside instead of just a bit more expensive but far more reliable Hall sensor system.
My guess is that it might be a main reason of SLA module failures. Most of them are reported at 30K-40K mileage, right after starting the car in cold mornings. Morning condensation along with a sufficient amount of conductive material accumulated between lamelles may cause position misreading.
The good thing is that it's possible to clean them using contact cleaner, which I did. By the way Chrysler says that it's non serviceable unit and wants more than 300 bucks for part only.
Here is his process to get to these contacts:
First check this tutorial - how to remove shiny bezels and shifter knob
1. remove chrome bezel
2. remove aluminum bezel and knob
3. remove rubber insert from the storage pocket
4. remove 4 Torx10 screws
5. Put shifter in N or D, detach wiring harness and remove shifter assy itself sliding it by shifter rod upwards, as I remember it's fixed by 4 screws or clips. Don't remember exactly, but it's straightforward.
6. Then continue at home, using anti-static precautions.
7. Remove soft plastic dust-shield (be careful, it's lubricated)
TOP SIDE OF ASSY
8. Remove 2 small screws and detach printed card board (PCB) from it's plastic chassis.
BOTTOM SIDE OF ASSY
Don't lose or break transparent acrylic lightguide (for illuminating PRND) at top plastic piece.
link to hi-res pics, sorry some of them are blurry (phone pictures)