In Mendix, the order of values in an Enumeration is not guaranteed to be preserved in DataGrid / DataGrid2 search dropdowns.Even if sorting is left as default, the dropdown options are often automatically sorted alphabetically by caption by the widget.
The inconsistent behavior you see is normal and can depend on:
widget type (DataGrid vs DataGrid2)
Mendix version
captions / translations
There is no supported setting to force the dropdown to follow the enum definition order.If the order matters, the recommended workaround is to use a reference entity with a SortOrder attribute or a custom filter instead of the built-in enum filter.