When cancel is used on a full buffed target (12 d/s up) it removes ONLY disco. (5 random d/s) 
When the number of d/s is getting lower, there is a chance to remove buffs (5x cancel on target with 8 disco we removed on avarage 4 disco and 1 buff) 
  
Cancel should remove 5 RANDOM buffs or disco, this is a major bug which impacts all nuker parties. 
  
I used chars lvl 85 for this tests. 
I tested with buffs from npc and buffs from a normal character also.