Options not set for link field uom

I get this error when trying to save my sales order. But when I delete the item and put another item. I can save without error. I crosscheck the item with my testing site, I got no error when saving. I also check if I miss filing the field in item. There’s no differences. Does anyone knows why?

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Please set the option of the UOM field. go to the customize form and set the options.