One locale code silently killed 92% of a Magento Shopware migration — and the tool reported Done

A Magento CE to Shopware 6.7.2.2 migration appeared successful, but about 92% of the source data never made it to the destination.

The failure came from Magento locales like zh_Hans_CN and zh_Hant_TW being converted into zh-Hans-CN and zh-Hant-TW, which Shopware does not have in its locale table.

That blocked language creation, broke sales channel setup for affected sites, and triggered cascading foreign-key and required-field errors for orders and customers.

The case shows how one unsupported locale mapping can silently derail a large e-commerce migration while still reporting success.