WLM2009: multiple convos get mixed up

I’m experiencing this issue. When having two or more conversation open, the first conversation’s messages end up in the other conversation (with another user) in an unpredictable way.
I’ve tried to perform multiple logins-logoffs without any significant improvement.

This happens on Windows Live Messenger 2009 on Windows 10 20H1 (compatibility mode set to Vista SP2).

Any ideas?

Same! For example: I chatted with my friend and then the another person
was in our chat. This was a private chat. I questioned him
but he didn’t answer. Escargot’s webpage says, wlm 2009 is unstable
right now and has got many bugs.

It is probably a bug caused by group chat.