The original mail has an alternative part consisting of an empty text part and multipart/related part.
Only that multipart/related contains HTML and picture (= Attachment).

Content-Type: multipart/mixed;
Content-Type: multipart/alternative;
Content-Type: text/plain
Content-Type: multipart/related
Content-Type: text/html;
Content-Type: image/jpeg;

multipart/alternative claims, that those two contained parts are exchangable.
So when SOGo replys it picks one of them.
I am not sure, if SOGo always picks the first one, or if that is dependent on the user setting "compose message in" either "Plain Text" or "HTML".
That said, SOGo's behaviour is correct here.

How did you create such an email?

The accounts that were used for the test were those of http://demo.sogo.nu/SOGo/
with the default editor.
You can try and reproduce the error.

I have same problem only in reply messages, forward working properly

version 4.2.0 nb 2020-01-02

Yes, the problem is only in replay, forward works fine since 4.1.0