We have been receiving this error on the server quite often on certain
user accounts.

When it occurs, I delete the account and then login via the website and
setup the account again.

This is getting really annoying. I have had to do it several times for a
handful of users.

Any ideas how to troubleshoot this or fix it for good ? Recreating the
account is just a workaround. The underlying problem is still occuring.
I have VERBOSE logging turned on, but only see this error and normal sync
operations with 0 items synced.

One thought... the users I have with the issue all seem to be in remote or
rural areas when it occurs. Maybe they are in the middle of an operation
or sync and the phone loses cell coverage. Just a thought. My users that
stay in town and always have coverage don't seem to be having issues.