12.1 RU5 manager updating but clients aren't

Bit of a strange one I came in and SEPM 12.1 RU5 was saying that latest defs were on the manager and matched symantecs but when I checked the def distribution report none of the clients had recieved any updates for 3 days. 

Anyone got any ideas of what could be causing this? 

SEPM is on 12.1 RU5 mixture of SEP 11 and SEP 12 clients reporting in (10,000+). Checked the SQL database more than enough space and plenty of space on the SEPM server. In the admin > servers I'm getting message An unexpected exception has occured which when I check the forums everything relates to no internet access yet the SEPM is pulling updates from the internet.