I have taken control of this manufacturing plant and killed the guardian. However, no corresponding materials were given to me after the end of this mission. I guess this may be the cause of the bug. It still tells me that I need to control it, but in fact it is already under my control.
The collection of the other two materials is available. I have not yet tried to control other manufacturing plants of the same type as the problematic manufacturing plant.
This is the Orichalcum Forge and as it is described in the text, this one is only needed to manufacture FROM this material but it doesn’t gather the material. To gather this material you need an Orichalcum Mine.
For every new material there are two types of sites, the “Resource gathering sites” to gather the new resources and the “Processing sites” that are needed for using these resources in the manufacturing process.
More Info is available here: http://wiki.phoenixpoint.com/Legacy_of_the_Ancients
Thank you very much for your reply, I understand now.
WOW this is way to complicated for a mid game event! Seriously you just don’t have time to for all this to build even a single weapon yet alone the sniper rifle which it is the only thing I am interested in from this DLC… I have just wasted two thirds of the game trying to figure out how to even get the materials. I have very little time left on the Dooms Day clock and I will not have enough time to build anything, looks like it will be a restart… I really hate that! It needs to be more simple, you get the location it starts producing end of story, BUT no you have build probs and WAIT scan areas and WAIT, find a location take it and WAIT… and then need you need to do this all again to find the other locations just to collect some materials and all the while you have to defend it and send manned ships to pick up the materials if you ever get any and you need to do this THREE times (once for every different material) seriously talk about beating about the bush, this is an entire game INSIDE a game! There just is not time for anything else, unless we can turn off the clock which should be an option anyway!!! … The other add on’s had it right you go in the cave kill the beaties and you get your armor/guns… Done deal very good! But this is just painful and we can’t get the rewards in time, well I can’t anyway and to me that’s all that really matters… RIGHT!
Yes, overly complicated 
