Hi, thanks for the report!
Unless a skill says "cannot be resisted", any detrimental effect it would apply is subject to a potency/tenacity check. This means that the game checks the relative potency of CLS and the tenacity of his target, and uses those values to determine the percentage chance that the target has to resist. The game will then use a random number generator to determine whether or not the target resists the effect.
Please note that resisting turn meter reduction effects has a baseline of 15% chance to resist, and cannot be reduced below that regardless of potency or tenacity levels.
So CLS might not reduce turn meter when:
1) The target resists the turn meter reduction effect
2) The target evades the attack
I hope this helps!
