Zero App - Menu - Category not selectable

Hi Balbooa,
Using the Zero App, I have single hierarchy of categories.
If I try to create a menu item for one of these categories, when I try to select an individual category for that menu, rather than a list of categories being shown, a pop-up containing the Joomla dashboard is shown instead?
This was a 2.17 site recently updated to 2.18.01.

Please see images.

Many thanks
Marc

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