Serious Application Core Data Error Swift3 - ios

Question

I am trying to get data from multiple apis and saving it to my coredata database. Earlier it comes once in ten times. but now i am getting it every time.
I have created a DispatchGroup and trying to hit api one by one. Below is my code.
let group = DispatchGroup()
group.enter()
SharedFunctions.getCourseSessions {
print("Course Session Done")
group.leave()
}
group.enter()
SharedFunctions.getCourseContent {
print("Course Content Done")
group.leave()
}
group.enter()
SharedFunctions.getCourseQuiz {
print("Course Quiz Done")
group.leave()
}
group.notify(queue: DispatchQueue.global(qos: .background)) {
print("All async calls were run!")
DispatchQueue.main.async {
ACProgressHUD.shared.hideHUD()
completrion()
}
}
Below is my fetching and saving data from api
class func getCourseSessions(completion: #escaping () -> ()) {
let param = "module=getCourseSessions&userid=\(User.uId)&Akey=\(User.akey)&schedule_course_id=\(User.scheduleCourseId)"
SharedFunctions.callWebServices(url: URLS.Base_URL, methodName: "POST", parameters: param, istoken: false, tokenval: "", completion: { (jsonDict) in
print(jsonDict)
DispatchQueue.main.async {
if ((jsonDict.value(forKey: "message") as! NSDictionary).value(forKey: "success") as! String) == "true" {
SharedGlobalVariables.arrayCourseSessions = (((jsonDict.value(forKey: "message") as AnyObject).value(forKey: "data") as AnyObject).value(forKey: "result")) as! NSMutableArray
print(SharedGlobalVariables.arrayCourseSessions.count)
// DispatchQueue.main.async {
SharedGlobalVariables.LoginBool = true
// get a reference to the app delegate
if #available(iOS 10.0, *) {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
print(SharedGlobalVariables.arrayCourseSessions.count)
for j in 0...SharedGlobalVariables.arrayCourseSessions.count - 1 {
let managedContext = appDelegate.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: "Course_Sessions", in: managedContext)
let courseSessionsScreen = Course_Sessions(entity: entity!, insertInto: managedContext)
if let arrData = SharedGlobalVariables.arrayCourseSessions[j] as? NSDictionary {
if let courseId = arrData.value(forKey: "course_id") as? Int16 {
courseSessionsScreen.course_id = courseId
}
if let userId = arrData.value(forKey: "user_id") as? Int16 {
courseSessionsScreen.user_id = userId
}
if let enableNextScreenSequence = arrData.value(forKey: "enable_nextscreen_sequence") as? Int16 {
courseSessionsScreen.enable_nextscreen_sequence = enableNextScreenSequence
}
}
do {
try managedContext.save()
// getCourseSessionProperties()
} catch let error as NSError {
print(error)
}
}
} else {
// Fallback on earlier versions
}
//}
}
completion()
}
})
}
There is no perticular place to crash app crash. it crash any where like above methode i am passing all apis.
Getting This error:
Error Domain=NSCocoaErrorDomain Code=132001 "(null)" UserInfo={message=attempt to recursively call -save: on the context aborted, stack trace=(
0 CoreData 0x0000000111ff3892 -[NSManagedObjectContext save:] + 306
1 Tuneem 0x000000010f64046c _TFFFZFC6Tuneem15SharedFunctions26getCourseSessionPropertiesFT10completionFT_T__T_U_FCSo12NSDictionaryT_U_FT_T_U_FT_T_ + 60
2 Tuneem 0x000000010f629197 _TTRXFo___XFdCb___ + 39
3 CoreData 0x000000011200cb52 developerSubmittedBlockToNSManagedObjectContextPerform + 178
4 libdispatch.dylib 0x000000011bf0205c _dispatch_client_callout + 8
5 libdispatch.dylib 0x000000011bee094f _dispatch_queue_serial_drain + 221
6 libdispatch.dylib 0x000000011bee1669 _dispatch_queue_invoke + 1084
7 libdispatch.dylib 0x000000011bee1b32 _dispatch_queue_override_invoke + 654
8 libdispatch.dylib 0x000000011bee3ec4 _dispatch_root_queue_drain + 634
9 libdispatch.dylib 0x000000011bee3bef _dispatch_worker_thread3 + 123
10 libsystem_pthread.dylib 0x000000011c299712 _pthread_wqthread + 1299
11 libsystem_pthread.dylib 0x000000011c2991ed start_wqthread + 13
)}
Error Domain=NSCocoaErrorDomain Code=132001 "(null)" UserInfo=. {message=attempt to recursively call -save: on the context aborted, stack trace=(
0 CoreData 0x0000000111ff3892 -[NSManagedObjectContext save:] + 306
1 Tuneem 0x000000010f64046c _TFFFZFC6Tuneem15SharedFunctions26getCourseSessionPropertiesFT10completionFT_T__T_U_FCSo12NSDictionaryT_U_FT_T_U_FT_T_ + 60
2 Tuneem 0x000000010f629197 _TTRXFo___XFdCb___ + 39
3 CoreData 0x000000011200cb52 developerSubmittedBlockToNSManagedObjectContextPerform + 178
4 libdispatch.dylib 0x000000011bf0205c _dispatch_client_callout + 8
5 libdispatch.dylib 0x000000011bee094f _dispatch_queue_serial_drain + 221
6 libdispatch.dylib 0x000000011bee1669 _dispatch_queue_invoke + 1084
7 libdispatch.dylib 0x000000011bee1b32 _dispatch_queue_override_invoke + 654
8 libdispatch.dylib 0x000000011bee3ec4 _dispatch_root_queue_drain + 634
9 libdispatch.dylib 0x000000011bee3bef _dispatch_worker_thread3 + 123
10 libsystem_pthread.dylib 0x000000011c299712 _pthread_wqthread + 1299
11 libsystem_pthread.dylib 0x000000011c2991ed start_wqthread + 13
)}
Trying to solve it from last couple of days getting no idea, any help will be appreciate.