So, after 212K miles of flawless performance, my transmission acts up. 

Yesterday it went into electronic limp mode with DTC codes 008 and 104, which translate to problems with the R/P solenoid in the console shifter.  I cleared the codes, but a few miles later it went back into limp mode.  Notably it started limping during a fast/bumpy turn.  Sure enough, opening up the console I find a wire (the cigarette lighter bulb harness had come loose) and some metal shavings (totally my fault) right up against the connector for that solenoid.  Codes cleared.  Happy days, right?

Well, after a days driving, it goes back into limp mode.  Grrr.  Must have missed some of the shavings, I thought.  But no!  Now it is showing DTC 013 and 109, which translate to problems with RPM sensor M3 inside the transmission.  Eh?!?  Normally these codes are caused by problems with the electrical conductor plate, a known weak spot on the 722.6.

So, now I'm left wondering, do I have a computer problem where it is throwing random DTCs? Or, did going into limp mode several times (very harsh shift into 2nd from 4th) damage the electrical conductor plate? 

Thoughts on how to proceed?

It definitely clears the codes.  It was in second gear limp mode and (after code clearing) went straight to normal operation.  I do agree that the conductor plate might be dying.  My current theory is that it was just waiting to fail and the extra jolt from going into limp mode pushed it over the edge.  Better at home than a thousand miles away.   The diagnostic unit is plugged in anytime I'm on the road now.  I can clear the codes at a stoplight.

50 miles more of driving, and the same codes (013 and 109), pop up just as I'm pulling into the neighborhood.  Every time it has thrown a code it was in a bumpy right hand turn.  Electrical plate and adapter collar ordered.  I've got a transmission flush kit that I was just planning on using.  I'm so glad I didn't.  I would have presumed that the flush brought the problem on. 

Anyone down my way know where to get this fabled Shell 134 ATF for a reasonable price?

Well, I got the new conductor plate and pressure spring into place.  No problems in the ~200 miles driven since then.  Many thanks to G-AMG for the nice writeup .  The whole process makes one a little nervous since one is working under the vehicle on parts that need to be kept very clean. 

On the cleanliness note: What needs to be kept clean is anything past the fleece filter.  Ideally, the pan should be kept clean, but it isn't really all that critical.  How do I know this?  Well, about 100K miles ago I had an unfortunate incident on a muddy forest trail where a stick pushed the transmission filler tube up and out of the transmission.  Eventually I spotted the dribbling ATF trail and pushed it back in.   As soon as I had the right ATF, I drained the pan and refilled it, but hadn't removed the pan until now.  It turns out that quite a bit of mud and dirt got into the exposed hole before it was closed up.  The pan had ~2 tablespoons of dirt and small gravel in the bottom.  No evident effect on the transmission though.  Even the magnets were pretty clean.