Couple of things to check:
-Is this a new setup?if not? what was the previous versions? Did you follow the proper update path...
diagnose cdb upgrade summary
-The version of your FGTs
-The time of your FAZ and your FGTS
-Do you get any realtime logs?
-any daemon has been crashed?
diagnose debug crashlog read
-create a back up for your logs and rebuild the DB
FMG-08 # execute sql-local rebuild-db
Rebuild the entire log SQL database has been requested.
This operation will remove the log SQL database and rebuild from log data.
This operation will reboot the device.
Do you want to continue? (y/n)
be very careful and make sure you create a proper back up of your config, DB and logs. Even create a snapshot of your VM too. and then rebuild the DB.
I would say create a ticket with the FAZ team to investigate the issue.