If you are upgrading your EEM environment and it is configured for mult-write then you should either....
1) undo the multi-write,
upgrade each EEM individually
then re-establish the multi-write after ALL nodes have been upgraded to the exct same version
2) shut off the other servers EEM servers and upgrade the EEM's one at a time.
If you have 3 nodes in your EEM multi-write configuration
server A, Server B, Server C.
Shut off B and C, upgrade A.
Shut off A, start B, upgrade B.
Shut off B, start C, upgrade C.
Start them all.
NOTE - We do not support any evironment where clients would attempt to have two different EEM versions configured in a multi-write mode.