We had similar issue to the one described in CSCvz71596 and CSCwd54400 on the 9.18(2)5 ASA code.
When creating new context, context subinterface assignment was not applied on standby unit and "Number of interfaces on Active and Standby are not consistent" message was seen in the log of the standby admin context.
Workaround was "write standby" on the active node.
