Same here. Re-joining by typing in correct user and pass.
Yesterday I updated to 9.502-4 version and I have the same problem
I tried to do a failed login, and log in again with the right credentials and I can not join into the domain.
"failed to join into a domain"...
Now my UTM is out of the domain, and I can not join it again :(
Having the same issue. Getting emails every 2 hours. No change has been made to any account or password. Started getting messages starting Sunday night 7/23/17 with Sophos UTM 9.501-5. Updated the firmware to 9.502-4 and restarted, still the issue continues. Ran a test to check authentication issue for admin and bind account both passed but the sync keeps failing.
Waiting to hear from support!
I thought I was cracking-up with this issue. I reported the issue a few months back, only for Sophos support to tell me that the problem must have been on my side. I didn't make any system changes which would cause the Synch issue to occur every two hours at exactly 39 minutes past the hour. Then today, after updating to 9.414-2, my users could no longer authenticate for the web filter. (Transparent SSO with AD) I had to disable the "Block Access After Failed Auth" in order to get past the issue. So I decided to dis-join AD, delete the computer account, and re-join. Now all appears to be working properly. Of course, I'll need to wait a couple hours to see if the synch issue disappears.