I was checking the online users and noticed that there was a username listed twice. I opened a new tab with both and it's the same user. I refreshed the page and it still showed them twice. I refreshed a couple more times and it finally went to only having them listed once. The user this was happening to was whitewolf15.

Most likely this user logged in from another IP, so there were two different active sessions within 15 minutes for the same user. We'll check if there's something else that can cause this.