1) Create a show and wait until show starts
2) Drag a track from below and place it under currently playing track (the green one)
3) Promptly delete the currently playing track
(you have to do it really quickly, but yet it's still within the frame of human's ability)
While GUI prompts that the dragged and dropped track is playing, it is not true.
Another song from the list is being played.
Surprisingly enough, the Ctrl+R -in the jplayer makes the inappropriate song be played with interruptions
Anyways, there is a workaround for this situation just delete any not currently playing track from the list and the correct order would be restored.