It seems there is a new error that i found on a few Fortigate firewalls: CFG_CMDBAPI_ERR
To fix the issue you can do 2 things:
1. Upgrade the Fortigate to the latest version
2. Reboot the IPS of the Fortigate (this is was it causing the issue). Below is the command(through CLI):
diagnose test application ipsmonitor 99
Hope it helps!