🔧 Amazon - Error "must have no element [children]", and the value must be valid.

Amazon error message (example):

cvc-complex-type.2.2: Element 'Width' must have no element [children], and the value must be valid.
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cvc-complex-type.2.2: Element 'StandardPrice' must have no element [children], and the value must be valid. 

What does this error mean?

Amazon is letting you know that they are receiving a width unit of mesure (for example: "CM"), but no corresponding value for the width. These two elements are mutually dependent, which incurs the error.

The issue can be identified in the Preview section: "item_width" is empty, whereas "item_width_unit_of_mesure" is filled in with "CM".

A similar error may occur with the price, if the price is empty but the currency ("EUR" for example) is populated.

Note: despite the word "children", this error has nothing to do with variations.

Solve and prevent this error:

In this example, add a rule to empty the "item_width_unit_of_mesure" attribute when the field mapped with the "item_width" attribute has no value. 

Rule example:

More broadly speaking, make sure that mutually dependent fields are either both filled in or both empty.