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ReviseItem: An error "Variations with quantity '0' will be removed" (ErrorCode 21916620) may be encountered when revising multi-variation items.
This may happen if you are adding a variation during revise but not passing the Quantity field.
Workarounds/Recommendations: Make sure you are passing the Quantity field for the variations that you are adding.
If your intention is to remove the item, then passing in the Quantity field is the correct procedure. Otherwise, if the intention is to make other changes to the variation, but to retain the variation as part of the listing, then it is required to include the Quantity field in the Variation container. Otherwise, the variation will be removed.