At the second attempt to open the Fortigate tunnel sub interfaces in the spectrum interface view, the tunnel interfaces disappear from One Click interfaces list
This is because of duplicates nodes in while building tree due to same vlan/tunnel/sub interface available in multiple hierarchies.
This issue is occurring when same tunnel available at 3rd level and 4th level
Release : 10.3
Component : Spectrum Core / SpectroSERVER
Code changes are merged in the 10.5 and in release 10.4.2.2