Make Null Disappearing

Currently having an issue tracking down the source of this problem:

Running Multiple cue lists triggered by multiple show control sources. The issue exists when I attempt to use Make Null. The system is set up with 8 partitioned cue lists and one that takes over everything at certain times, but some times it wants to take over with exceptions. Make Null work's perfectly when I play it back, but then after some programming it seems to have lost it's Make Null instruction. I have noticed after moving a range of cues before the instruction it seemed to disappear. I'm wondering if it's an issue involving Blocks, but can't track down the specifics in the moment.

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