[SPOILER] Inventory and weapon slot problem

[MasterWizard7]

So, the last few days I saw a "problem" at my weapon/warframe slots. On my inventory page it will display for example one(1) open slot but when I tried to claim weapons from the foundry it told me that I had no more open slots and I must buy weapon slots. The same goes for my Warframe slots.

I know that existed a similar thread in the past for weapons requiring other weapons for the crafting posses but still it does not emplane the waframe slot.

Thank you for your patience.

Edit:

Spoiler

The displayed open slots at the inventory were for the completion reward for The Sacrifice Quest.

 

Edited January 9, 2019 by MasterWizard7
Understood the cause of the problem. And added the Spoiler.