Solved
Dedicated MGMT and L2 Mode Isolation
On my FG firewall I have defined MGMT as OOB / dedicated management, and the firewall is in L2 / Transparent mode. One interface PORT1 from firewall is connected to the switch VLAN-1 and MGMT on the same switch VLAN-1. In this case is there a possibility of L2 loops formation on Switch?