Linnworks cannot automatically switch an item on Amazon between FBA and FBM. Due to how FBA listings are identified in Linnworks, there is potential for error if an FBM item gets switched to FBA or the other way around, so this approach is not recommended.
We have also seen cases where switching an item between FBA and FBM would lead to "phantom" or "ghost" listings on Amazon. Information on Amazon Seller Central forums suggests that in such cases a seller adds the item to their Amazon inventory or switches it between FBA and FBM, but on the offers page, it appears as though there were two offers for the same item from this seller. The biggest problem is that one of these offers - the "ghost" or "phantom" listing - does not appear in the Seller Central inventory, so the seller cannot control its available level, which can lead to overselling.
1. Linnworks will only find out that the item is no longer FBM and needs to be marked as FBA when it receives a new listing report from Amazon. This is done on a daily basis and can be ordered separately by clicking the Download Listings button in Amazon channel settings.
2. Until the report has been processed, Linnworks will still see the item as FBM, as it was previously, and will submit stock levels for it if there has been a change in available level.
3. This is how stock levels could be submitted for items that have just been switched to FBA in your Amazon inventory - potentially resulting in phantom listings on Amazon, even if you switch the FBM listing back to FBA via the Amazon inventory.
We advise against switching items between FBM and FBA in the first place and recommend using one SKU for the FBA item and a separate SKU for the FBM item.
This resolves the problem with Linnworks not knowing that the item was switched to FBA - it will not be required as there are already two separate SKUs. It will also prevent the potential problem with phantom or ghost listings on Amazon.