When a node using the content translation paradigm performs translation initialization (meaning, the source node is moved from "language neutral" with no translation set, to the site default language + a translation set), the EntityTranslatableInterface::getSourceLanguage() method begins to return the language of the last imported piece of content, rather than the actual source language.
This is only made apparent when multiple XLIFFs for different languages are being imported for a single entity within a single request thread.
When a node using the content translation paradigm performs translation initialization (meaning, the source node is moved from "language neutral" with no translation set, to the site default language + a translation set), the
EntityTranslatableInterface::getSourceLanguage()method begins to return the language of the last imported piece of content, rather than the actual source language.This is only made apparent when multiple XLIFFs for different languages are being imported for a single entity within a single request thread.