How can I make VSCode properly display french (and other languages) html text when I open the file when UTF-8 and Windows-1252 format doesn't work?

Question

Context:

I work with many translated languages as part of my job (Send file to translation firm and then receive the translated versions), so this also applies to other languages as well.

1. I am the original author of the HTML files returned.
2. My HTML files are created with UTF-8 (VScode settings is read & write UTF-8).
3. The HTML files received are UTF-8.
4. VSCode's GuessedContent format offers UTF-8.
5. UTF-8 format reads "�".
6. Windows-1252 format reads "�". [Updated] Tried that since it is one of the solutions I found online.
7. That same, untouched, file displays correctly on Notepad.
8. Copy-pasting the files content from Notepad to VSCode works.
9. The issue happens on a sometimes-basis when opening files received from an other firm.
10. Encoding default is already set as UTF-8 for reading and writing.

What I tried so far:

-> Manually changing the format of the file and reopening it from UTF-8 (received format) to Windows-1252 (french) and vice-vera. The issue persist as the error remains coded in their respective format.

-> Install the french language pack to see if it would help with at least the french projects, but still no help. French is not an issue as I work in a french speaking environment. I can type it myself.

-> The translation firm we work with says that they see the files correctly on their end.

-> My colleagues who uses other programming software (like Sublime Text) do not have this issue

-> Decoding the error text does not keep in memory which error is what (when Notepad can)

-> This post (1) mentions that VSCode and Identity Services Engine services (CISCO probably)(2) aren't the most compatible, and it is quite probable that my workplace and/or the firm uses these services. Maybe it could lie here?

(1) https://github.com/PowerShell/vscode-powershell/issues/1680#issuecomment-453200280

(2) https://www.cisco.com/site/ca/en/products/security/identity-services-engine/index.html

What can be done?

Images for support

1. Code as seen in Notepad
   

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2. Code viewed from Sharepoint (where the file is downloaded from)
   

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3. That same code displayed in VSCode
   

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4. It is currently UTF-8
   

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5. How VSCode ends up displaying the code
   

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6. Typing over the file with the problematic letters appears correctly.
   

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7. Codepoints do not recognise the different errors even though Notepad does. (left: file read by Notepad, middle: said file uploaded onto onlinetools.com, right: same error code for all 4)
   

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8. Comparing the error code to the supposed code
   

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