WORKAROUND 1:
Please ensure:
1.- The Domain Controller used by the ARS service is pingable.
2.- Telnet from affected ARS server to DC port 135 and 389 is successful.
3.- Run NSLOOKUP to diagnose Domain Name System (DNS) infrastructure:
NSLOOKUP
set type=all
_ldap._tcp.dc._msdcs.oup.com
WORKAROUND 2:
Ensure the Administration Services added to the affected managed domain are set to the correct AD site or pointing to an available/correct Domain Controller. If a change is required here, the ARS service will need to be re-started:

WORKAROUND 3:
If after following WORKAROUND1 and WORKAROUND2 the issue still persists, and the DS.log shows error 8000500D which means the directory property cannot be found in the cache for some reason, then follow below steps:
1.- Enable ARS Verbose Logging
Note: Please rename any existing DS.log file so that a new DS.log file is recreated.
2.- Close the ARS MMC Console
3. Stop Quest ActiveRoles Administration Service.
4. Clear ADSI Provider schema cache: go to \Program Files\Common Files\Quest Shared\ArsAdsiTempFiles and delete all Files.
5. Start ARS Service
6. Open the ARS MMC console and confirm the issue has been resolved.
7. If the issue still occurs, raise a new service request with support and provide the new set of logs.
Note: Remember to disable Verbose logging once logs have been provided to avoid disk sizing issues from happening.