I was just ready to post the same question...
I have the exact same problem with my 2018 Pacifica Touring-L (non hybrid), but with both iphones and Android based phones.
Pairs ok, then after 30min with the vehicle off, loses all the phone paring data. (Also the "VR" button will cause the system to lock up 50% of the time.)
Took it to the dealer and they diagnosed it as a bad "radio" (U-Connect system/radio) and ordered a replacement.
3 weeks later, still no replacement. After getting Chrysler Care involved, it turns out Chrysler cancelled the order because "other users had reported this problem and there will be a software update 1st quarter of 2018 to fix it."
I find it hard to believe that every 2018 model sold with the premium sound group (Alpine stereo) has this problem and it is not a bad radio unit plain and simple. I just want it swapped out with a working unit so I can actually use a phone in the car. (It is illegal in my state to use a cell phone that is not hands free)
I was willing to give Chrysler a pass on this issue as losing cell phone pairing is something that probably would not be tested during the assembly, and the dealer would not test it either. Only the buyer after driving it off the lot would use it.
We are thrilled with everything else about the Pacifica, and does seem to be a world-class vehicle, however the service if you have an issue seems to fall far short of satisfactory.