Add me to list. I live in New Hampshire, USA and just before Thanksgiving, picked up a 2014 REX, plain model with just heated seats. Primary use, 40 mile round trip per day work commuter car + local driving. At 660 miles had drivetrain malfunction warning come on (still said driving possible but check in with service). I had been running REX about 70+ miles on a return leg from a long trip during a heavy rainstorm. Car did switch to REX mode ok even when turned off/back on (one extra refuel stop later).
Next day, took car to dealer. Dealer had car 2 days (did the 4 hour run the REX dry out mode) - they also wanted to do a 50 mile road test strictly REX mode but I had another trip that I knew I could run REX > 50 miles on return leg. Went on the trip the next day, had the same warning a second time, again after about 70 miles strictly on REX again on a return leg, same message. Continued driving car home. Stopped at a Chargepoint, chared about 12 miles worth of battery, Continued on and car switched to REX mode again ok but still had same error message.
Following day, car ( now 908 miles) was in shop 2+ weeks and root cause identified as moisture in generator unit [rex electrical machine fault from moisture buildup] ; storage at assembly site contributing and the vent on generator inadquate to allow any trapped moisture to escape. New generators have a modified vent. My car received: AT Starter Motor Generator, Sealing Sleeve , Compensation Ring, Compression Spring, Splined Torsion Shaft, Core Return, Torx bolt. I had to wait for seals to come in...all in all a 2.5 week repair. Since the repair, I now have 1600+ miles on car, running REX >60 miles on some trips, during rain, sleet, ice, snow, -5 deg weather, the usual fun New England weather challenges. No further issues. Also had the KLE replaced, reprogrammed, per service bulletin while car was in the shop.
The entire incident reminded me of my first Volvo (a V-40) that was a semi lemon - Volvo ended up buying back but it was the great service / support of dealer that made that all work out).
My dealer response was outstanding. Immediately offered to give me the BMW 220VAC home charger unit I was planning to buy - I did not even ask for anything in return for my discomfort. Loaned me a 650 grand coupe for 2 days on first repair and 320i for second repair period. Service manager as well as service advisor called/emailed me at every turn to keep me informed. Probably helped this was my 5th BMW with this dealer and 2nd one in 14 months (wife & I did a European delivery on 2014 Z4 Sept 2013. Really enjoy the car, getting lots of interest from folk....fun to drive. Never had any customer support issues with the dealer with any of the five cars I've had the pleasure of owning.