Getting Infinite Golden Keys Bug

I’ve used 3 SHIFT codes that were supposed to give me 8 golden keys. After I used them I claimed all available keys in my mail box. However, even after claiming the keys and despite the fact that I haven’t used any other codes, I still receive SHIFT mails with Golden Keys attached to them. This has been happening non-stop and I don’t know what may have caused it and how i can stop it. Thanks.

“Bug” lol

What’s this code and how can I get this glitch?

Lol they are from the diamond lootbox edition. The codes are listed in IGN’s site.