I and a friend have been getting these errors since Monday or so.
Sorry to come back to this, but repairing the folder only gives temporary relief.
After a few of these errors, google goes into “user over quota” and then “repair” does not work anymore.
This is a google apps account. We have 2-factor authentication, but a normal gmail account, even with 2-factor auth. is syncing fine.
Thanks for any help you may provide!