Once you list an item and preview the shipping plan, you might encounter an issue where the shipments are bound for separate locations.
If you've accepted this Shipment plan:
Then you need to fulfill it accordingly by creating 3 different boxes and sending them to the respective locations, while also doing the Box Content process.
Learn more about it here:
https://accelerlist.helpjuice.com/en_US/box-content/what-is-box-content
If you think this plan isn't feasible, then in very rare cases, you can consider deleting the Shipment plan, but that does not go over well with Amazon as you will be violating Amazon's TOS if you do it often.
If you delete the existing plan, you can create a new one by previewing Shipment plans for the batch marked as 'Completed' in AccelerList.
If the new plan is feasible, then you can accept it, reject it and try again later.
There's also an option in Seller Central for an additional fee per product, you get to decide where your products will go. It's called the FBA Inventory Placement Service.
Learn more about it here: