Level 12 or 13 of the proficiency upgrades for armour and weapons requires 0/0 exotics. For the weapon, if you have no exotics it will not allow you to upgrade it. when you have an exotic, 1/0 it will upgrade.. so, even though the requirement is zero, you must have at least one exotic component to go past it.
Hey @nevvyn,
Sorry to hear about that, could you please provide some screenshot showing this or a short video if possible ? You can upload it on the sharing website of your choice and send us the link here.
This would help us understand the issue better, and we'll be able to contact the dev team for more info.
@nevvyn Thanks for getting this video for us! I've gone ahead and passed this information along to the team. As soon as I hear back or have any updates, I'll be sure to update this thread and let you know. 
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