This error is two-fold.
The SKUs are grouped differently on the marketplace than what they are in Product Catalog.
Example: SKUs A, B, and C are all on the same variation listing on eBay. However, in Product Catalog, SKUs A and B are together. However, SKU C is separated and has its own Product page.
You are trying to have the listing data on the marketplace be in sync with Product Catalog. Whether that is images, titles, etc, it does not matter.
Three different solutions, depending on what you want.
1. Merge and split the Product to match what you have on the marketplace. Once the Product matches what the marketplace has, the error will be resolved.
2. Merge and split the marketplace listing to match what you have on Product Catalog. Once the marketplace variation group matches what Product Catalog has, the error will be resolved.
3. Edit the marketplace fields (in LM) that are in sync with Product Catalog and change them to something different. This will cause the field to no longer be in sync with Product Catalog, and the error will be resolved.