[2020] Adrestia SR1 - How to acquire

Have been trying to get this for months now and it never drops. I get the BT access card, I open weapons crate in the secret room on the Hovercraft and yet I have never once received this weapon. I've tried all the suggestions I can find online yet it never drops, I just get some random crap weapon.

I want to build the Nemesis. So is there a particular trick to getting this to drop or this just another bug that UbiSoft will ignore and will never get fixed?

And no, I don't already have the scope in my resources.