Hi ND,
"Thumbs up" to the above advice. Different releases of SEP client will be acceptable (though I recommend always updating to the latest version) but all SEPMs have to be at the same build. Here's the official article on the subject, which applies to SEP 12.1 as well as SEP 11:
About Maintaining Consistency of Software Versions throughout a SEP 11 Organization
Article:TECH131660 | Created: 2010-01-13 | Updated: 2010-12-13 |
Article URL http://www.symantec.com/docs/TECH131660
...
Maintain a Consistent RU Level on all SEPMs
If there are multiple SEPMs in an organization, a consistent version of the software should be maintained upon them all. Replication failures and other complications will arise if separate sites are operating with different releases of the database schema.
For the benefit of future admins who have this same question, please do mark the thread as solved if the advice above contains the information needed! &: )