Perhaps you have one of the repeat modes enabled - Repeat Current Item or Repeat Playing Now. "Repeat Current Item" will always repeat the played track. "Repeat Playing Now" will repeat the played track if you have only one track in Playing Now.
Top menu > Player > Repeat > ...
or click the Repeat button to set the mode:
EDIT
mojave posted while I was writing my reply.
To the right of the progress bar are the repeat options. Is this set to "Stop after each item"?
This would stop - not repeat.
In General/Behavior do you have Double-Click set to "Replace Playing Now: (all)?
I have Double-Click set to "Add Playing Now (to end)". I use Playing Now actively and I prefer to keep the tracks that are already there in the playback queue and add the new tracks to the end. When I want to play a track immediately or next I use the right -click > Play or right-click > Sent To > Play >... options.