You won’t need a save to reproduce this. If you have fast adaptation on a ranged character and they shoot at a target obscured by an environmental feature rather than a character, then fast adaptation doesn’t proc.
Basically shooting at a character behind a frontline and missing will always proc the perk. Shooting at a target hiding behind a tree won’t proc the perk on a miss.
I kind of just factored this into my gameplay for ages but then thought “According to the description of the perk, I’m not sure it’s supposed to work this way”.
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