Brand Registry + Old UPCs

I’m currently undergoing a Brand Registry Application that is pending.

Back in 2016ish I added a whole host of Amazon FBA products with GS1 UPC’s that were purchased on eBay from a reseller. (This was kind of common practice back then if I remember right, and there were tons of anti-GS1 talk everywhere.)

The products have been selling under said UPCs with my Brand Name/Manufacturer Name since that timeframe without issue.

Now as I understand it, Amazon cracks down on UPC mismatches. Will my Brand Registry application unearth the fact that these older listings are not UPC’s that I personally registered with GS1 and cause delisting?

How can I get ahead of this? Can the UPC’s be changed? Relisting is not really an option – these are old listings that are keyword leaders.