Finally picked it up today. Was ready Tues. but today was the earliest (for me) they could get me. Here's what was caused the car to get stuck in 5th on Sunday.
"found EGS fault code 4ps1 trans position signal disruption. Reads improper position. Pulled up center console and inspected conectors, found harness to be under tension due to porr routing. Corrected harness rout and reassmebled. Checked connections at transmission, ok. Cleared faults and test drove."
So it was a wiring problem from the shifter to the transmission, and they rewired it. Drove it to work, then home. Ok so far.
I hope this is it, 'cause though I was disgruntled, by the time I was getting home, I was looking forward to driving it tomorrow.
Thanks for the encouragement, all.

 

Good luck - seems like a relatively minor cause to your problem. Glad it wasn't anything mechanical - enjoy your new baby!