SEPM 12.1 upgrade

Hello all,

Happy Newyear to all of you.

I have a question about automatically upgrading clients to the latest version of SEP from the SEPM.
I recently upgrade to the latest version of SEPM 12.1 RU2, and im attaching the new clients to some of my groups to test the functionalty of the new SEP clients 12.1.2015.2015.

Strange thing is some of the clients upgrade to the newest client and some don't even after a few weeks they still didnt upgrade to the client i attachted to this group.
Does anyone know why this behaviour is happening?

Thanks,

LEVD