I decided to join the forum after reading about this issue.
I had the same issue with my 1-week-old moment. The battery life on the phone was lasting for 3-5 hours and the phone was having random shutdown issues. In my case, I installed youmail on the phone on the first day of ownership. In addition to youmail, I installed around 20 app’s, so deciphering the culprit app or the possible of having a defective phone would have taken awhile.
After reading this post and following the advice provided by the prncssmelissa in the removal of youmail, the problem has went away.
The phone is now stable and I see an immediate improvement in battery life. Today after removing the youmail app, I am still running on last night charge (over 15 hours with light to moderate use). I am using the factory battery that has been conditioned properly.
In addition, I notice the phone is no longer overheating. As noted in the post, it looks like the youmail app was causing the processor to run a full speed in addition to preventing the phone from going into standby.
I closed my youmail account after reviewing the response. For now, I will use the stock voice mail app.
Big Thanks to Melissa for documenting the issue.