Trying to save data from JSON into Coredata

Using Swift
1

Hi!
After parsing a JSON file I want to save its content into CoreData.I am using this code bellow but I am getting 2 records out of 3.557

func saveToCoreData(){
    let vinylDB = VinylsDB(context: managedObjectContext)

    for vnl in vinyls {
        vinylDB.id = Int16(vnl.id!)
        vinylDB.title = vnl.title
        vinylDB.artist = vnl.artist
        vinylDB.label = vnl.label
        vinylDB.isout = vnl.isOut
        vinylDB.vinylAudoID = vnl.vinylAudoID
        vinylDB.vinylCountry = vnl.vinylCountry
        vinylDB.vinylLocation = vnl.vinylLocation
        vinylDB.vinylID = vnl.vinylID
        vinylDB.year = vnl.year
        vinylDB.vinylFormat = vnl.vinylFormat
        
        DataController().save(context: managedObjectContext)

    }
    print("end")
}

func save(context: NSManagedObjectContext) {
    do {
        try context.save()
    } catch {
        print("ERROR saving DATA")
    }
}

what am I doing wrong? Thank you