unrecognized selector sent to instance when using Swift fetch - ios

Question

I'm using Xcode Version 8.3.3 with Swift 3. My phone is running iOS 10.3.2.
This issue is happening while I'm out using the app.
I have an intermittent error occurring in my phone app. Once data has been uploaded to a web service, the following code is called to update the object in Core Data. I'm not seeing why the object is causing an error:
func uploadedMarker(_ oldRouteId: Int16, stepId: Double, newRouteId: Int16) {
do {
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "HoldMarkers")
let routePredicate = NSPredicate(format: "routeId = %i", oldRouteId)
let stepPredicate = NSPredicate(format: "stepId = %f", stepId)
request.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: [routePredicate, stepPredicate])
request.returnsObjectsAsFaults = false
let markers = try self.context.fetch(request) as! [HoldMarkers]
if markers.count > 0 {
let marker = markers.first!
marker.uploaded = true
marker.routeId = newRouteId
do {
try marker.validateForUpdate()
self.appDelegate.saveContext()
}
catch {
let nserror = error as NSError
NSLog("uploadedMarker - Core Data Error - Updating HoldMarkers :\(nserror), \(nserror.userInfo)")
}
}
}
catch {
let nserror = error as NSError
NSLog("uploadedMarker - Core Data Error - Fetching HoldMarkers :\(nserror), \(nserror.userInfo)")
}
}
Context is defined as:
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
Like I said, this is an intermittent error:
-[MKPolyline _genericValueForKey:withIndex:flags:]: unrecognized selector sent to instance 0x17049a860
1 CoreFoundation __exceptionPreprocess + 124
2 libobjc.A.dylib objc_exception_throw + 52
3 CoreFoundation -[NSObject(NSObject) doesNotRecognizeSelector:] + 136
4 CoreFoundation ___forwarding___ + 912
5 CoreFoundation __forwarding_prep_0___ + 88
6 CoreData _PF_Handler_Public_GetProperty + 244
7 Foundation -[NSFunctionExpression expressionValueWithObject:context:] + 736
8 Foundation -[NSComparisonPredicate evaluateWithObject:substitutionVariables:] + 224
9 Foundation -[NSCompoundPredicateOperator evaluatePredicates:withObject:substitutionVariables:] + 440
10 Foundation -[NSCompoundPredicate evaluateWithObject:substitutionVariables:] + 272
11 CoreData -[NSManagedObjectContext executeFetchRequest:error:] + 2796
12 Parks-Tracker RouteViewController.uploadedMarker(Int16, stepId : Double, newRouteId : Int16) -> () (RouteViewController.swift:1371)
13 Parks-Tracker #objc RouteViewController.uploadedMarker(Int16, stepId : Double, newRouteId : Int16) -> () (RouteViewController.swift:0)
14 Parks-Tracker RouteViewController.(updateRoute(Double, longitude : Double, timestamp : Date, routeId : Int16, stepId : Double, segment : Int16, complete : Bool) -> ()).(closure #2) (RouteViewController.swift:1114)
15 Parks-Tracker thunk for #callee_owned (#owned NSDictionary, #owned NSError?, #unowned Int16, #unowned Double) -> () (RouteViewController.swift:0)
16 Parks-Tracker thunk for #callee_unowned #convention(block) (#unowned NSDictionary, #unowned NSError?, #unowned Int16, #unowned Double) -> () (RouteViewController.swift:0)
17 Parks-Tracker RouteViewController.(callRouteUpdate(Double, longitude : Double, complete : Bool, routeId : Int16, stepId : Double, segment : Int16, conditionDescription : String, markerImage : NSData?, routeName : String, destinationId : Int16, completion : (NSDictionary, NSError?, Int16, Double) -> ()) -> ()).(closure #1) (RouteViewController.swift:1262)
18 Parks-Tracker thunk for #callee_owned (#owned Data?, #owned URLResponse?, #owned Error?) -> () (LoginViewController.swift:0)