I think this happens because missing unique tag:
```
<property name="Tags" value="weapon,gun,sideAttachments,ranged,holdBreathAiming,smallTopAttachments,barrelAttachments,mediumTopAttachments,largeTopAttachments,reloadPenalty,attPerception,perkDeadEye,canHaveCosmetic,rifleSkill,attachmentsIncluded,M1"/>
```
This is from Silent but deadly(gunHandgunT0PipePistolWL_Legendary:
```
<property name="Tags" value="weapon,ranged,firingMode,sideAttachments,holdBreathAiming,reloadPenalty,shortRange,pistol,smallTopAttachments,magazine,perkGunslinger,PipeGun,PPLeg,unique,handgunSkill,attachmentsIncluded"/>
```