
Explanation:
Given that there is little connection between the two clouds when site A is down and cause an evacuation I would say directory server is damaged causing domain issues. 1 - Directory Server.
SCADA system controls the pumps so 2 - SCADA. Last is route flapping that is VPN concentrator, now dont make the mistake i did put 3 in site B not A as for the added option used the BGP routing, if bgp route is set to go through site A that might cause issues so 3 - VPM Concentrator (Site B) (BGP route option).