Question: I tried to redeem an item for XP, but the interface disappeared and I've lost functionality. What should I do?
Answer: This will happen your Armory contains more than 1,750 loot items, and you will need to restart the game.
Return to the Armory after restarting the game. You will then see that the loot item was redeemed and the XP was rewarded.
This will continue to occur as long as more than 1,750 loot items are in an Armory. Select the All Loot filter in the Armory to see your loot item total.