It’s a known issue, see other threads here about it. Elektron say it’s with a small batch of buttons that had the wrong thickness edge or something. I don’t quite believe that, because I assume a “batch” of buttons like that would be in the thousands. Then again, it’s not happening to everyone (and hasn’t to mine). Anyway, all you can really do is get Elektron To sort it out, which they will when they come back.
Edit: I guess if it’s within the return window of whoever you bought it from, you could get a replacement, and hope it’s not part of the bad batch.