The Giftbox Notifier list has a limit on displayed gifts. Any gifts beyond the limit are still available but will only display after claiming/removing items from the list and logging out then back in.
Keep in mind that just because Michael is no longer a Community Manager does not mean issues are not being forwarded and addressed internally. Michael was a large influence on that, and his work in the area among many others is appreciated, but current game-related issues are not the topic of discussion.
Something to consider is the size of MapleStory. After over a decade, there is an enormous amount of content - both universal and GMS-exclusive - and accounting for every single factor becomes more and more difficult over time. While the hope is for everything to function correctly the first time, as a program issues will arise and be addressed appropriately. It's unfortunate when we must incur additional downtime to address issues, but what's important is that issues that come to light due to the dynamics of the playerbase are being addressed - not pointing blame over factors which are not always obvious from a testing standpoint.