Error 21916626: Variations Specifics and Item Specifics entered for a Multi-SKU item should be different.

Typically, this error occurs for redundancy between the variation specifics and the item specifics in a multi-SKU listing on eBay. To avoid, check for overlap in specifics: use variation specifics to differentiate between the versions of the product (such as size, color, etc.) in the VariationSpecifics field, and use item specifics to describe common attributes (such as brand, material, etc.) in the ItemSpecifics field.