Same UPC Tied to multiple ASINs

So we sell a 6 pack of tea on Amazon (we are the registered brand owners) and have sold it for years via FBA. We also want to start selling single boxes of the teas, and we see there are already ASINs created for the singles on Amazon – with active 3p sellers and sales history – great!

However – when we search the singles in “add a product” via the UPC – both the single (that we want to sell) and our 6 pack (that we already sell) appear, and the UPC/GTIN is the exact same on both in the backend. So – we realized that our 6 packs which were listed years ago were listed with the UPC for the singles.

If we add the singles to our catalog – will this cause issues since they have the same UPC associated with them on the backend? We’ve actually been sending in our 6 packs for years to FBA using manufacturer barcode with no issues. Our plan was to add the singles to our catalog, and then send them in using Amazon fnsku barcodes to avoid any confusion with them getting checked in under the wrong ASIN. Is this a viable way to proceed, or is there a better solution?

Thank you!