What changes were made to the fanout model from 9.4.3 on and why it was made / what problems were seen that led to this change
In 9.4.3 changes were made to the fanout model so that each connection to it will be treated as a separate fault record.
So in case if all the devices connected to fanout goes down for each fault record, fault isolation will generate multiple unresolved alarms on FI model except for the fault record having an alarm already existing.
There was an issue with fanout as it can find root cause on any of the device in fault record which might not be appropriate if fault records are not separate.
It led to above changes in Fanout.