The problem was already described here: Strange structure behaviour in 2.3.2
The fallback works if you set the complete field to translate: false, not just a field within the structure. For a subfield based translation fallback to work, the Panel would have to store the values of the default language in all non-default languages. But I’m not sure this would make sense, considering that you can remove entries from a single language but not the others with such a setup or reorder them. This would all end up in a big mess, I think.
In your particular case you can probably work around this issue if you set the title as image meta data and make the complete field untranslatable (so that you would only select the images to be used and their order in the default language). In that case you can then opt for another field type (for example, the images plugin) instead of the structure field.
Or maybe you can describe your exact use case so that we can try to find a better solution.
Edit: If your structure field contains sections for the home page, consider using subpages or modules. To make handling of these subpages/modules easier, you can use the index. field or the sortable field.