Although you restarted the FMC/FTD, I would try to restart the sftunnel between the FMC and the FTD, if that should not help, I would go to TAC to fix this issue.
> expert
admin@fmcv-05:~$ sudo manage_procs.pl
Password:
**************** Configuration Utility **************
1 Reconfigure Correlator
2 Reconfigure and flush Correlator
3 Restart Comm. channel
4 Update routes
5 Reset all routes
6 Validate Network
0 Exit
**************************************************************
Enter choice: 3
1
**************** Configuration Utility **************
1 Reconfigure Correlator
2 Reconfigure and flush Correlator
3 Restart Comm. channel
4 Update routes
5 Reset all routes
6 Validate Network
0 Exit
**************************************************************
Enter choice: 0
Thank you
admin@fmcv-05:~$