remove "fext-ipsec" interface

Hi,

I tested a FortiExtender LAN Extension on an FGVM-02. After removing the Extender configuration, only the tunnel interface remains, which cannot be deleted. The error message is:

(phase2-interface) # delete fext-ipsec-***
Can not delete a static table entry
Command fail. Return code -61

Does anyone have an idea how I can remove it?

Thanks.