All units in same shippment, same inventory, same listing & half of the units don't correspont with their ASIN

I had 1000 units earbuds sent to Amazon FBA, all with the same bar code, the listing has been checked and everything was listed correctly. There was no problem with the shipment, they got all 1000 units.

I start selling them on Amazon, I'm a brand registry as well. All good, the listing is active with the Amazon corespondent ASIN and they are selling.

Then out of the blue, I receive an email saying that 450 units are not corresponding with any ASIN (so same barcode doesn't correspond with the ASIN given by Amazon). Of course I've contacted the seller support team straight away explaining that this is impossible. I had 1000 units with the same barcode and ASIN. How is possible that 450 units not to correspond with the ASIN, same listing, same barcode, that means same ASIN for all 1000 units. At present I am selling the 550 units ( so these are corresponding with the ASIN) but not the rest because they became unfulfillable ( they don't correspond with the ASIN).

They kept replying to me that this is under investigation and to wait patiently. Today I've received at my home address 49 units without creating any removal order from my side and the case still being under investigation.

This situation has became so frustrating and it literally consumes me.

Has any of you experienced such situation? I'd appreciate your reply if you've been in similar situation.