diamonds – question mark in month names translations

Translating month names in greeks, I get diamonds/question marks.

I think the problem is related with the encoding of the page. The theme is utf8 encoded and it works fine without qtranslate-x. When I change the encoding to Windows-1253 I can read the month text but the rest of the text is got scrambled.

Any recommendation ?

Regards,

https://www.ads-software.com/plugins/qtranslate-x/