Child references in Firebase being changed for unknown reason - swift

Question

I am currently working on a project that involves uploading cards to a database. I am using Swift 4 and using google's firebase as the database. I have made the code function for placing cards from your hand onto the playing area, but when they are moved from one tile on the playing area to another tile it creates a duplicate of the card instead of moving the card that is already there. From closer inspection I have found that this is because the snapshot.ref in the retrieveUpdates method does not retrieve the correct reference value of the card that is already in the database. That causes it to call the code to create a new card.
My question is thus: why are the values of the snapshot.ref changing between when they passed by one used and received by another?
//Sends a card and location to the database when a card is moved
func updateDatabase(playingCard: PlayingCard) {
let cardUpdate = Database.database().reference().child("Updates")
//This takes the location that the sender dropped the card.
if let location = game.location(from: playingCard.card) {
if case .battlefield(let field, let stack) = location {
//If the card is already in the database it should keep its old ID but if it is new it should be assigned a new ID
let reference = playingCard.databaseRef ?? cardUpdate.childByAutoId()
let updateDictionary = ["Sender": String(playerNumber),"Card": playingCard.card.name, "Field": String(field), "Stack": String(stack)]
if playingCard.databaseRef == nil {
playingCard.databaseRef = reference
reference.setValue(updateDictionary)
}
else {
reference.updateChildValues(updateDictionary)
}
}
}
}
func retrieveUpdates() {
let cardUpdate = Database.database().reference().child("Updates")
cardUpdate.observe(.childAdded) { (snapshot) in
if snapshot.childrenCount != 0 {
self.processUpdate(snapshot: snapshot)
}
}
cardUpdate.observe(.childChanged, with: { (snapshot) in
self.processUpdate(snapshot: snapshot)
})
}
func processUpdate(snapshot: DataSnapshot) {
let snapshotValue = snapshot.value as! Dictionary<String,String>
let cardName = snapshotValue["Card"]!
let sender = Int(snapshotValue["Sender"]!)
let stack = Int(snapshotValue["Stack"]!)
let relativeField = snapshotValue["Field"]!
if sender != self.playerNumber {
let fieldNumber = (4 + sender! - self.playerNumber + Int(relativeField)!) % 4
var foundCard = false
for playingCard in self.gameGraphics.cards.reversed() {
if let databaseRef = playingCard.databaseRef, databaseRef == snapshot.ref {
foundCard = true
self.currentPlayingCard = CurrentPlayingCard(playingCard: playingCard, startPosition: playingCard.position, touchPoint: playingCard.position, location: Location.dataExtract())
}
}
if foundCard == false {
let card = self.gameGraphics.addFromDatabase(name: cardName, field: fieldNumber, stack: stack!, scene: self)
card.databaseRef = snapshot.ref
self.currentPlayingCard = CurrentPlayingCard(playingCard: card, startPosition: card.position, touchPoint: card.position, location: Location.dataExtract())
}
self.touchUp(atPoint: self.gameGraphics.allBattlefields[fieldNumber][stack!].position)
}
}
Any help would be greatly appreciated. This is one of my first programs written in swift so my coding practices are still not very good.
Here is the scene did load.
override func sceneDidLoad() {
super.sceneDidLoad()
anchorPoint = CGPoint(x: 0, y: 1)
FirebaseApp.configure()
let login = loginInfo()
Auth.auth().signIn(withEmail: login.username, password: login.password) { (user, error) in
if error != nil {
print(error!)
} else {
print("login Successful")
}
}
retrieveUpdates()
}