ZCM 11.2.3a Won't Always Register w/ ENGL on XP Machines

We are using ENGL in conjunction with Zenworks. I'm having a hard time getting my Windows XP machines to register with my Zenworks server after we moved to 11.2.3a. Windows 7 x64 machines seem to always register without any issues. Trying to reimage the XP machine over and over again finally works, but here's some of the registration errors we are seeing:

zac.log contents:

1st:
Processing Command: reg


Unable to register with the server at: https://<server.name>>.
Service Error. code: -21, message: Could not determine device type from <OS>
tag: unsupported

2nd:
Processing Command: reg


Unable to register with the server at: https://<server.name>>.
RegistrationManager - Network error connecting to server: Unable to connect
to the remote server

3rd time worked

4th:
Processing Command: reg


Unable to register with the server at: https://<server.name>>.
RegistrationManager - Network error connecting to server: Unable to connect
to the remote server

5th:
Processing Command: reg


Unable to register with the server at: https://<server.name>>.
RegisterUser - Unable to register with any service