Why are all sessions used by SYSMAN?
You mentioned system copy. Whenever you change the ipaddress or hostname, DBConsole goes haywire, and even the official solution is to recreate it as described in:

How to configure Dbconsole After the Ipaddress or hostname of the Machine has Been Changed or if the hostname ipaddress is going to be changed? (Doc ID 1333938.1)

The usual steps to do this:

emca -deconfig dbcontrol db -repos drop
emca -config dbcontrol db -repos create