You are definitely asking in the right place
Being mono-lingual, I would never have triggered your issue. All I can offer is ideas to track down the error (and maybe the cause). The code Gurus will probably then have a fix once they know exactly all the steps (and settings) that will reproduce an error.
Your initial report was lots better than some we see here
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If you have a small sample (pre conversion) and the same file converted that fails to validate, you might open an issue on the Bug tracker (link in the help) outline you system configuration, and the exact steps you took.
Attach the files to the bug report.