Tracks are auto-added to playlist - not wanted

[geoslake]

hi

I've been using vlc for quite a few years, but for now many months, when i drag&drop tracks on it, they are added to the playlist.
When I wanna open another track, it plays the first again (the 1st from the playlist, that is), so that i have to use the "next track" button.
The weird thing is that it doesn't happen everytime.

Please note that i use the portable version (from portableapps.com), so it may be related to this version only (but i guess it shouldnt)

thanks