I'm at a loss.

I need to customize "defaulteventicaldialog.php" to delete some export options and to optimize layout.
First I've tried to code the original file directly, second I've tried using overrides (templates/et-notarix/html/com_jevents/helpers/...).

But nothing (really nothing!) works - exactly no effect at all doesn't matter what changes are applied.
As a result it always shows original layout / options. It seems as if the view of somewhere else is used.

Insane: even deleting all files inside "components/com_jevents/views/default/helpers" doesn't have any kind of effect.
Of course, cache has been deactivated.

Could please someone give me a hint what I'm missing?