HTP with effects

I am attempting to create a flame flicker effect. I am using two cue lists running at the same time that effect the same channels (to make the effect more random). Both cue lists are using the random 2 effect but have different size, rate, and offset. I would like to set both cue lists to HTP, but when I do that, the intensity output remains static at the the base level of the channel with no effect. Thoughts? Am I missing a better way to do a flicker effect that has no obvious pattern?
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