What is the problem with incorrect encoding of variables in php2word when saving in Word (eng)?

Question

Windows

Essence of the question: There is Windows 10 English (license), there is Office 2010 in Russian.
There is a script on the site that takes variables from the database and inserts them into the .rtf
document. *) in question marks (naturally, only data in Cyrillic) .
I throw the file to a friend with Russian Windows, he stupidly saves it to a new one, I upload it to the server - everything is ok.
Wherever possible in Windows, the Russian language was added. Does not help.