Prevent DoT Stacking
 

I haven't been able to find information on this, and I have failed to figure it out. I have two DoTs that stack, and I'm trying to prevent this from happening. One is a copy of the other, so the effect ids are the same (except the value). I've messed with spelleffectindex, spellgroup and rank. Dot_stacking_excempt is set to 0 (No). I'm not sure what I'm not getting right. Can anyone point me in the right direction?