You need to be aware of all of your agent plug-ins. For example, which plug-ins are enabled, which plug-ins are you upgrading, and what are their dependencies.

All plug-in policies are disabled during upgrade, so you need to turn them on.

Any plug-ins that are not upgraded may cause conflicts with newer software. A best practice is to upgrade all components at the same time to ensure full compatibility

Read these

STEP 1: Prepare for the upgrade

12. Disable all agent and plugin install and upgrade policies for clients.

13. Disable all agent and plugin install and upgrade policies for Site Servers.

For more follow the attach pdf

Attachment(s)

7.1 to 7.5 Quickstart Upgrade Guide_0.pdf   710 KB 1 version

Some Upgrade documents

ITMS 7.5 installation, upgrade, and migration prerequisites

Altiris 7.1 to ITMS 7.5 How-To Upgrade Video

https://www-secure.symantec.com/connect/videos/altiris-71-itms-75-how-upgrade-video

I think you should disable the Plug-in Policies but not the actual Patch Polices.
 

1. If you don't want any additional activities and load on your NS Server, such as patching managed endpoints, which aren't yet upgraded to latest 7.5 version of SMA and Solution plug-in, then you can disable "SWU" policies (Patch policies).
2. As far as I see, default resource target of staged "Patch" policies, includes managed endpoints with 7.1.x version, where SMA or Software Update plug-in isn't yet upgraded to latest 7.5 version, therefore they will able to receive these patch policies and perform patching.

• Example of default resource target of patch policy:

• And what is a query for managed endpoints to be included there: