I have a major bug to report, and a solution. If you create a Redeem event which can be claimed multiple times by the same user (let's say 2 times), if the user opens multiple tabs of the redeem code link, such as forum.example/currency/db-credits.1/redeem/?code=THECODEHERE he's able to claim it indefinitely, as long as the tabs are open at the same time. A simple way to do so would be clicking with the mouse wheel on the link (which immediately opens a new tab in the browser).
I think that part of the script should be tweaked.
Another bug (which was already reported and you can finally fix thanks to the info above) is the fact users can claim the "Daily Activity" reward multiple times every day, just by refreshing their browser many times when 24 hours passed since their last login. The concept is identical, the script isn't able to determine the user already claimed it because each claim happens at the same moment, so I hope my information helped you and you can finally fix two important bugs using the same method, thank you.
PS: If you'd be so kind to let me know via PM how to fix it by myself, so I can also apply it to my custom version of your add-on, I would be grateful, as I'm good with php but I'm not having enough time to inspect all the code recently, due to personal reasons.