Since I installed Ubuntu 16.04 LTS, VLC 2.2.2 will systematically open video files in 2 separate windows: video in one, audio (equalizer sound bars) and controls in the other.
VLC is set as the default player, so I can simply click on files to summon vlc to open them (always in 2 separate windows, unfortunately). I made sure Tools > Preferences > Interface > Playlists and Instances were set to allow only one instance and one instance when started from file as suggested in other threads addressing trouble when opening several files at once, which is not my case.
This thread on Ubuntu Forums provides a workaround for the bug affecting 2009 versions of both Ubuntu and VLC, which likely won't apply to either in 2018 (I'll try if no more obvious fix is suggested). If this is just a "settings" problem, I don't know what it is, as VLC is pretty much unchanged from the default downloaded version. Any ideas?