Mines stuck in 3rd too :-(
Hi, another brit here.
JC 5.7L Limited on 60,000ish miles
2 nights ago it was cold and icy (2c) and I was gonna drive home from work. Whilst pulling away I noticed the car was shuddering and driving really slow, then I realised it was stuck in 3rd gear! Going from N to D made the car jump forward and was instantly in 3rd gear. Restarting didn't help. Pushing left and right did nothing, except holding the stick to the right made it display 'D' but was actually still stuck in 3rd. Letting go just flipped back to '3'. Managed to get home but the check engine light came on during the journey. DTC code P0700.
Next day, engine light is still on but looks like I can use it as normal (not driven it but no longer selects '3'). Taking it to Jeep tomorrow, will let you know what they think. I suspect the cold weather had something to do with the problem. I've only had the car 2 months so I really hope this is a one off!
Jeep Commander 5.7 HEMI Limited in black with Autogas conversion.