Fortigate 30E blocks SSH Connect by Key

Dear Fortinet Users

I have a 30E up and running, when I want to connect to any server in the cloud e.g. Amazon EC2 or Oracle OCI Compute by SSH key, then I get this SSH error back. 

When I do the same SSH connection at work or by GSM, then it works. Is this a problem of the SSH inspection?

Regards, Martin