Accented characters in HTML documentation

We are trying to make Github automatically generate the HTML documentation for MobilityDB-workshop
https://github.com/MobilityDB/MobilityDB-workshop
using the following workflow
https://github.com/MobilityDB/MobilityDB-workshop/blob/master/.github/workflows/generate_docs.yml

In the resulting HTML on Github Pages
https://mobilitydb.github.io/MobilityDB-workshop/
the accentuated characters have been replaced by ï

When generating in my local machine the documentation using the same command
xsltproc --stringparam html.stylesheet "docbook.css" --xinclude -o index.html /usr/share/xml/docbook/stylesheet/docbook-xsl/html/chunk.xsl mobilitydb-workshop.xml
the characters are correct as shown in the following screenshot

Any idea how to solve this?

Thanks in advance

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Prof. Esteban Zimanyi
Department of Computer & Decision Engineering Â(CoDE) CP 165/15 Â
Universite Libre de Bruxelles     Â
Avenue F. D. Roosevelt 50 Â Â Â Â Â Â Â
B-1050 Brussels, Belgium        Â
fax: + 32.2.650.47.13
tel: + 32.2.650.31.85
e-mail: 
Internet: http://cs.ulb.ac.be/members/esteban/
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