If you place down a Weapon Manufacturer as EV2 if will not Update its damage in game, only the inspection will tell the damage it should do.
This means you cannot buff it and changing equipment won't affect already placed WMs.
Steps to reproduce:
1. Have no Relic in the Weapon Manufacturer Slot
2. Place it down (dummy will work)
3. Put Item in the WM Slot and inspect it
4. Watch the real damage dealt to enemy's staying at the base value.
I can confirm this, because of this bug it is not possible to buff the WM.