Solution : https://service.sap.com/sap/support/notes/626272 (SAP Service marketplace login required)
Key words : 
job_rstlanupg upgrade phase terminates, terms upgrade reason, error_message system exception, cp <langcd>/de/, pat <transdir>/eps/, spda_prepare_patch function module, iv_patch = <space> parameters, relevant language subdirectories, language packages, language cds
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