Enforced Threat on the Fighter tank doesn't always put you at the top of the threat list. Instead, your threat remains the same. Unfortunately, it's difficult to give a description on how to replicate it because this bug happens at seemingly random times. The best I can think of is if you use Block or Dig In, or another encounter power, too soon after using ET you may be accidentally cancelling the effect of the power but it still goes on cooldown.
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