Realm accessed from incorrect thread occasional - swift

Question

I have this function
class func addCVals(_ criteres: [[AnyHashable: Any]], _ type: String) {
DispatchQueue.global(qos: .background).async {
autoreleasepool {
if criteres.count > 0 {
if let realm = DBTools.getRealm() {
do {
try realm.transaction {
let oldValues = CriteresVal.objects(in: realm, where: "type = '\(type)'")
if oldValues.count > 0 {
realm.deleteObjects(oldValues)
}
for critere in criteres {
let cval = CriteresVal(critere, type)
if let c = cval {
realm.addOrUpdate(c)
}
}
}
} catch {
DebugTools.record(error: error)
}
realm.invalidate()
}
}
}
}
}
The request that get oldValues occasionally cause an error
Realm accessed from incorrect thread
I don't understand why as I get a new Realm before with this lines:
if let realm = DBTools.getRealm()
My function getRealm:
class func getRealm() -> RLMRealm? {
if !AppPreference.lastAccount.elementsEqual("") {
let config = RLMRealmConfiguration.default()
do {
return try RLMRealm(configuration: config)
} catch {
DebugTools.record(error: error)
DispatchQueue.main.async {
Notifier.showNotification("", NSLocalizedString("UNKNOWN_ERROR_DB", comment: ""), .warning)
}
}
}
return nil
}
CriteresVal is an RLMObject that is composed of this:
#objcMembers
public class CriteresVal: RLMObject {
dynamic var cvalId: String?
dynamic var type: String?
dynamic var text: String?
dynamic var compositeKey: String?
override public class func primaryKey() -> String {
return "compositeKey"
}
private func updatePrimaryKey() {
self.compositeKey = "\(self.cvalId ?? "")/\(self.type ?? "")"
}
required init(_ cvalue: [AnyHashable: Any]?, _ type: String) {
super.init()
if let values = cvalue {
if let cvalId = values["id"] as? String {
self.cvalId = cvalId
} else if let cvalId = values["id"] as? Int {
self.cvalId = "\(cvalId)"
}
self.type = type
if let text = values["text"] as? String {
self.text = text
}
}
updatePrimaryKey()
}
func generateDico() -> [String: Any] {
var dicoSortie = [String: Any]()
if let realm = self.realm {
realm.refresh()
}
if let value = cvalId {
dicoSortie["id"] = value
}
if let value = type {
dicoSortie["type"] = value
}
if let value = text {
dicoSortie["text"] = value
}
return dicoSortie
}
}
compositeKey is the primary key which included cvalId and type
Thanks for help.