My Galaxy Note 4 was "upgraded" to Marshmallow today and I immediately started getting the popup notification "Unfortunately, IMS Service has stopped." This occurs as a popup about every two seconds, which effectively bricks the device. The problem occurs even if I boot into Safe Mode.
Things that have not helped:
- restarting after taking the battery out.
- wiping the cache for the Messages app.
- changing my default messaging application to Messages+.
- wiping the cache partition.
- checking for application updates.
- uninstalling Facebook Messenger.
I found this thread which suggests turning off "rich communications," for an S5 Neo, but the Galaxy Note 4 doesn't appear to have that option anywhere.
At this point the only thing I can think of is a factory reset, which I'd very much like to avoid.