Some Scope sights models has two skins (A, C, D and E), which regulate what sight they will use (new after June's patch or old)
If you want to change that sight on the gun's bodygroup, use SubMaterial tool for this.

How to make a turned on flashlight?
You may use Glow Material addon for a white emissive texture.

Physics/collision on some small props are wonky
I'm aware of this issue. If there will be no solution, I'll make them as an effect rather than physical prop.

Weapons has bones to regulate some small parts. Use Advanced Bone Tool\Ragdoll Mover\Joint Tool to manipulate those