We had a similar issue, and under guidance from Cisco TAC we were asked to CLI on to the secondary FMC and run 'manage_HADC.pl' and select option 6 (re-establish' mirror. This took about 10 minutes to complete but seemed to do the trick.
Under guidance from Cisco TAC we were asked to CLI on to the secondary FMC and run 'manage_HADC.pl' and select option 6 (re-establish' mirror. This took about 10 minutes to complete but seemed to do the trick.