Error format in XML doc under OpenOffice

I got the same error message:

"format error in the sub-document file content.xml at position 2,225608 (row,col)"

I tried GNUMERIC, it didn’t work (couldn't open the file). I tried Peone's method, that didn’t work either; except that I still managed to repair my file thanks to Peone!
I started like Peone:
- Change the file extension from .ods to .zip
- Download and install Context available here: https://www.clubic.com/telecharger-fiche10500-context.html
- Edit the file content.xml with Context

Except that after I went to line 2, column 225608 (as indicated in my error message). There I recognized the text from my file, I knew pretty much where we were.
And not far from there I spotted two weird things:
- line 2, column 225820:

<text:span text:style-name="T55">􀂾 </text:span>

In XML, there can't be 􀂾 between ">" and "<"
=> I deleted 􀂾 and replaced it with a space;
- line 2, column 226625:

<text:span text:style-name="T55">ô€‚</text:span>

Same, I deleted ô€‚

The difficulty was finding these "weird things" (because already the accented letters seem weird, but that's normal). They are near the indicated line and column (2,225608), but not exactly there!
I spotted these "weird things" by opening the file content.xml with Mozilla Firefox (there you can see them better, they appeared as hieroglyphs, not far from the place suggested by the error message)

There you go, it’s a hassle, I don't know if it will work next time, but it's worth a try.

Hello Peone and Xu
thank you very much for allowing me to save my .ods work file (5 hours non-stop... imagine the number of changes). I had a duplicated "font bold" property and that was blocking the opening of my file.
Collaboration is great!! As a result, I signed up and will do my best to help the next person.
Good evening.

Hello, I have the same problem with xmlns:fo="urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0" but not just with xmlns:fo but also with xmlns:script="urn:oasis:names:tc:opendocument:xmlns:script:1.0" and others!

What exactly should I remove? Only xmlns:fo="urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0"
or the entire line with, for example, xmlns:script each time "urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0" appears?

Another problem: how can I modify the content.xml document integrated in the ZIP archive of the ODT?
I have installed Context but the difficulty is extracting the .xml and reintegrating it into the archive. I am using Peazip
Thank you for your help....