A couple days ago i got an achievement for 12 years in Subeta and a Loyalty box, and just a couple minutes ago when I went to my user preference page I got the same achievement again and an another Loyalty Box.
[flower=Jaona]
If I'm remembering right, you can get multiple at a time if you missed checking for an anniversary? I think? Idk?

The loyalty box is very specific to the time you joined. So lets say you joined May 9th at 6pm. You wouldn't be able to collect yours for the year until 6pm. It is possible you may have missed one from the previous year? I would honestly make a ticket as that is more of an item issue and a UA or programmer would be able to look into it.
Dexter by ❤