Clients getting Applications and Packages, but NOT Software Updates

Question

I am trying to set up a new SCCM2012 installation and have come across a strange problem that I need help on.
We have a single primary site at one location with distribution points at several other locations. Clients at some of the locations (but not all) are able to get deployed applications and packages from their DP, but for some reason are not able to get Software
Updates from the same DP.
When I look in the LocationServices log, I can see it contact the DP when an application is available. The following appear in the log:
Current AD site of machine is XYZ
Calling back with the following distribution points
Distribution Point='https://<My DP>...,Locality='LOCAL',DPType='Server',Version='7958', etc.
Calling back with locations for location request {<CID>}
But otherwise, the LocationServices log is filled with:
Current AD site of machine is XYZ
Calling back with empty distribution points list
Current AD site of machine is XYZ
I don't understand how the machine is able to locate and work with the DP for Applications/Packages, but not for Software Updates. I'm thinking it must be something with the boundaries/boundary groups, but I have checked and everything seems to be fine,
and they are working for Apps/Packs. 

Answer 1

The WindowsUpdate.log seems to indicate that it is talking with the MP:
**START** Agent: Finding updates [CallerId=CcmExec]
*Include potentialy superseded updates
*online=Yes;Ignor download priority=Yes
*Criteria="(DeploymentAction=* AND Type='Software') OR (DeploymentAction=* AND Type='Driver')"
*Search Scope={Machine}
+++++ PT: Synchronizing server updates +++++
+ ServiceId= {<CID>}, Server URL = <My MP with appropriate port>
Agent * Added update {<CID>}.202 to search result
* Found 289 updates and 77 categories in search; evaluated appl. rules of 2711 out of 4339 deployed entities
** END ** Agent:Finding updates [CallerID=CcmExec]
But there is no mention of my DP.