The sights are not lined up. To fix this, drag and drop weaponheavyshotgun.meta provided or
edit it in mods\update\update.rpf\dlc_patch\mplts\common\data\ai

Search "FirstPersonScopeOffset" and replace the 2 rows with this

<FirstPersonScopeOffset x="0.000000" y="0.105000" z="0.015000" />
...
<FirstPersonScopeRotationOffset x="-0.050000" y="0.000000" z="0.000000" />