Seems this service is causing hellfire for my phone right now (iPhone 6s + on TMobile) running iOS 10 (14A5261v). Cant open the iMessage settings and iMessage will start out the day working as intended but start to fail later in the day. The service shows 99-100 utilization in Instruments and ~32:17.964 of CPU time.
I tried to go through and sign out of a bunch of services:
iCloud - (takes forever but eventually does sign out)
iTunes/App Store - (same as above)
iMessage - cant because wont let me get into the settings to sign out
FaceTime - finally got in to sign out
Homesharing - Not signed in
Facebook - Signed out
Twitter - Signed out
Vimeo - dont have
Flickr - dont have
Spotify - dont have
and service is still crazy. Any other ways to stop/reset the service to have it be refreshed like new? I restart the phone frequently and it doesnt do anything. Any other ideas? Putting in a bug report as well.