One problem related to wiring has been reported for the 2012 Mercedes Benz R350. The most recently reported issues are listed below.
"takata recall" - while driving along a county street my vehicle completely stalled. I put in park and it started and went approximately a 1/2 of a mile and stalled again. It did this twice more before I got home where I shut it off and called a tow company to take it to the shop. My service advisor call and told me that the wiring hones to the engine burned up.