adding productvariation -> translation -> SKU already in use

Scenario:
Product in default language_A with:
Productvariation-a SKU 111
Productvariation-b SKU 222

Translated to language_B

All is working fine
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Add Product variation
Product in default language_A with:
Productvariation-a SKU 111
Productvariation-b SKU 222
Productvariation-a SKU 333

goto Translation language_B

no way to add the variation -> SKU 333 already exists