Job errors with books containing MathML

From a user report:

> While using Pipeline-ui, almost all the EPUBs containing MathML fail to convert to DAISY using EPUB to DAISY (TTS Enhanced) script.
> - Errors like
> WARNING - While processing sentence with ID id_1: AUDIO_MISSING: could not find any installed voice providing the language 'en' (Please see TTS log for more info.)
> - More errors that I forgot to copy.
> - Running for a long time and no result.
>
> I have selected a Microsoft voice in Settings and haven't changed any options.
>
> - Mathematical Optimization for Machine Learning
> https://www.degruyterbrill.com/document/doi/10.1515/9783111376776/html
>
> - Topics in Complex Analysis
> https://www.degruyterbrill.com/document/doi/10.1515/9783110796810/html
>
> - Demystifying Artificial Intelligence
> https://www.degruyterbrill.com/document/doi/10.1515/9783111426143/html
>

Start by reproducing the failure with one of the listed EPUBs using the EPUB to DAISY (TTS Enhanced) script, then inspect the TTS log alongside the AUDIO_MISSING warning. Compare behavior for EPUBs containing MathML and confirm that the conversion completes successfully with the selected Microsoft voice.

Written by the indexing model from the issue text.