Text attachments converted from UTF-8 to ANSI

I am using EM Client version 8.2.1659 om Windows 10 for reading Gmail.
I recently noticed that text files, which were attached with UTF-8 encoding have been converted to ANSI. Since those files contained some Cirillic content, this content was garbled. If I downloaded them from Gmail’s web interface, they contained correct encoding.

I there a setting I missed or is this a bug?