As i remember this bug was already posted few months ago, but it only works on NAGC, now because of the patch for Mari an upgrading bug in GCPH is now able.
Instructions:
1. Upgrade any necklace or guard anklet.
2. Press Esc and when you press Esc that will remove the black background while your upgrading, even though the elena graphics is still there, you can already press upgrade button again.
Here are the screen shots that prove that this is true:
THIS IS NOT A BUG THAT MAKES YOU UPGRADE YOUR NECKLACES AND ANKLETS WITH OUT FAILING. IT IS A BUG THAT LETS YOU UPGRADE FASTER.
This have been tested working only for GCPH