solution would be to transfer the content in that case to one of these storage overflow meta items
(even though that is exploitable then i guess)
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Attempts to spawn a filled blueprint deleted from the catalog results in dropped items and can not add items to an incomplete blueprint missing from the catalog.
WORKAROUND: If a new blueprint with the same name and layout is re-uploaded to the catalog then the previous blueprints will regain their function.
https://youtu.be/lFvAU3Ls7KI
WORKAROUND 2: If you can not remember the exact layout to recreate the previous blueprint you can recover the items from a partially filled blueprint by blueprinting a ship core under the partial filled prints name then you can continue to fill the partial print and once complete attempting to spawn it will dump the items in space.
https://youtu.be/ePLho3ZLLks