Unusual catalog issue: When adding new GTIN-exempt SKUs, Amazon is mistakenly adding them under existing ASINs. Should I just bite the bullet and get UPCs for all variants to solve?

I have an existing parent ASIN. I am uploading new GTIN-exempt SKUs to my catalog via flat file. Then I am I moving them under that parent as variants.

The problem is that Amazon is adding many of them under existing ASIN numbers, essentially creating duplicate ASINs. This is obviously a no-no, so I’m having to delete these and try to upload again.

Context: I’m trying to add 80 variants of size and color, and it’s taken days to even get to 50% of the way through, and fewer and fewer are uploading successfully.

I suspect this is because the SKU, color, and size nomenclature is very similar, i.e. Amazon’s catalog AI probably thinks they are one-and-the-same and need merging. I’ve tried varying field nomenclature to get successful uploads, but it only had a limited impact and I’m back to square one.

Should I just bite the bullet and pay for UPCs for all 80 variants, so that Amazon is clear that these are separate products?

Has anyone experienced similar issues or have thoughts on whether UPCs will solve the issue? TIA