Item specific contains multiple values where one expected

Error 21919309 fires when an item-specific is submitted with multiple values but the category only allows one. The listing is blocked.

Feeds sometimes submit comma-separated values ('Red, Blue, Green') for a single-value specific, or pipe-separated lists for color/size when those should be variation specifics rather than item specifics.

1. Identify item specifics that are single-value-only per category.
2. Pick the primary value and drop the rest, or move secondary values to other fields.
3. If the multi-value list represents variants, move them into Variation Specifics.
4. Use eBay's GetCategoryFeatures to confirm allowed cardinality per specific.
5. Resubmit once values are corrected.

• Submitting 'Red, Blue' as Color when Color is single-value in that category
• Pipe-separating values that should be variants