I can't seem to find this listed in known issues or maybe i'm just dumb but Queenbreaker's Bow is not proccing Unstop Fusion for me when its picked in my artifact. I noticed this when i was playing in the Nether and was running into only unstop champs on expert mode. I swapped to a different linear and it procced right away so Linears in general work i guess.
(i even tried to spot check taking the catalyst away, changing firing modes, and also unselecting particle deconstruct to see if any of that was being weird with it and still didn't proc unstop at all)
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It won't stun them if you use it on its 3 round fire mode.