ProxySG just does not boot up after being loaded with 184.108.40.206 and rebooted.
Reverting back to previous version brings ProxySG back to life.
Other symptom seen by other customers were also hang and unresponsive.
This is caused by a health check bug B#54461 which would be fix in 220.127.116.11.
Workaround steps are as below.
1. Archive all configuration
2. Policy Reset (clears all policy)
3. Delete all authentication realm
4. Attempt to upgrade to 18.104.22.168
5. Restore backup/policy
Note: The fix is not released yet at the time of this writing.