Got the same issue.
I had a new Touchpad and created a new profile there, because in my country (Austria) they do not have pay-Apps in the Appcatalog.
Everything worked fine and still does. I got pay-Apps and everything.
I got a new Pre3. I added it to the Touchpad profile. Worked at first.
Now it constantly reboots, sometimes even while I speak on the phone. It is just Luna restarting, so the talk on the phone wasn't even interrupted.
Another thing that disturbs me about the PRe3: the mobile hotspot does not always work. My Touchpad does not always find the hotspot, and even if it does, the Pre3 sometimes continuosly "connects" and "disconnects" the TP ... that's not very funny. The Mobile Hotspot worked fine on my Pre Plus with the TP as well as other devices.
All in all I am happy with my Pre3, but those issues are a bit of a PITA ...
I do not really wanna re-doctor a NEW phone and I actually would not like to set up ANOTHER profile with my TP to connect my Pre3 to.
Would be nice if that issue could be fixed differently...