I found the solution for this issue but cannot explain why it's working when using tilde before. Maybe because the system is in another sequence/keystroke until…
The issue is, that iTerm uses option + number to invoke the "To switch split panes" command (bottom left corner "Navigation Shortcuts" section). If you remove the key from the settings or use another one, the special chars are working as expected again. Unfortunately you cannot distinguish between the right and left option key for this shortcut so I use the following config:
- To switch split panes: cmd + number
- To switch tabs: No shortcut
- To switch windows: No shortcut
This way I can navigate the split panes with cmd + number and navigate the tabs using cmd + left/right arrow.
This was driving me crazy since weeks :-/ Hope this helps someone!