LEAP 15.1 X session remains unlocked after switch user

My environment:
LEAP 15.1
kde-plasma

I log in with my user (say user-A), I do "switch user" from the Energy/Session menu, and start a session with another user (say, user-B).
When I do "switch user" again to come back to the initial session of user-A, the session remains unlocked!!!
I would expect that it asks me for the password.

Strange enough, this only happens with user-A. If I do "switch user" and go again to user-B session, then it always asks me for the password.

I have been researching config files and forums but I can't fix this. I believe there must be some configuration setting in some file of my HOME folder that forces this behavior for my user.

Any help will be appreciated!!

Thanks