I've gotten this error twice now. after seeing this pop up,I went to the software updates icon and made sure it was connected to my wifi, but it continued "scanning" and did not proceed to the next stage.
I got the same error 2 days ago. After the error my stereo started staying on after I shut off and exited the car which was unusual. Today when I stopped briefly for a coffee I came out and it said 89% updated please don’t drive. I had to drive anyway but it finished updating Uconnect. I don’t think it used WiFi since I wasn’t near any known networks. Seems to be random. I was listening to siriusXM for the last few days prior to the update so it gives credibility to the theory it uses that service for updates. I typically don't listen to SiriusXM