Hopefully this is in the correct section of the forum, if not, feel free to move the topic and give me a slap on the wrist. xD
So, a small bug that's come to attention is using the Armor Upgrade coupon, which was received in one of the Popo Gift Boxes. It's advertised in the description as a free upgrade (+12) that lasts for 2 days, though it seems to be bugged when I attempt to use it.
I would provide screenshots but due to the server being a little glitched I can't do that at this very moment.
Regardless, what happens is basic enough. I go to the Upgrade Merchant, and ask for a strength upgrade. I then put the armor in, which happens to be level 8 gear. I have checked to make sure that it does not have any upgrades, so that the item should work. Next, I put the coupon in, which again, is apparently a guaranteed success +12. When I click upgrade, the card DOES show up, though attempting to click it does nothing.
None of the buttons on the screen work after this point. I am still in game, able to type in the chat, even view the map, but I can't access the logout button, nor can I edit my inventory or move around. Essentially, I'm stuck in the upgrade menu unable to do anything until I restart the game entirely.
I have yet to try upgrading gloves to a higher level with the Weapon Upgrade coupon, but I assume it would potentially do the same thing. I'll give an update if no-one else does as soon as I can.
EDIT: After some browsing through the forum I've found this bug is actually already addressed in multiple places. Whoops.