When I add a package to a group, many times the clients do not update but...

...when I add the client and manually by either pushing it from the SEPM manager or via the Client Deployment tool, clients will update.

I have created a group specifically for the purpose of upgrading. I add all of the pacakages for 32 and 64 bit systems and I think one mistake I made was letting it run only for one day, I have now changed that to 365 days hoping it would make a difference. I still notice though that doing it this way only works on occasion, and some clients NEED to have me manually push the package via the client deployment tool.

Any ideas why this may be happening?