No icon ("\f107") shown in the menu

Hi All Since quite a while I have the following issue: In the main menu the "V" ("\f107") and the search icon are not shown when the page is entered. Only after selecting a menu entry, everything works fine. The behavior is identically on Firefox, Edge or a mobile browser (requesting the desktop site). The problem is persistent even after several updates of the theme. Inspecting the element with Firefox shows the "\f107" in the ::after identically in both cases. Deactivating f107 makes the "V" disappear and the placeholder... Anyone has some idea on how to fix this issue? Thanks a lot and best regards Jan