Hi I am seeitng the same issue. It is only with iOS 12 and started happening with Beta 5.
(lldb) thread select 1
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
* frame #0: 0x0000000108b6ba66 libsystem_kernel.dylib`kevent_id + 10
frame #1: 0x00000001087d63b9 libdispatch.dylib`_dispatch_kq_poll + 222
frame #2: 0x00000001087d6f3b libdispatch.dylib`_dispatch_event_loop_wait_for_ownership + 516
frame #3: 0x00000001087c59cf libdispatch.dylib`__DISPATCH_WAIT_FOR_QUEUE__ + 315
frame #4: 0x00000001087c5427 libdispatch.dylib`_dispatch_sync_f_slow + 231
frame #5: 0x0000000106cfc284 CoreData`_perform + 244
frame #6: 0x0000000106cfcc33 CoreData`-[NSManagedObjectContext(_NestedContextSupport) newValuesForObjectWithID:withContext:error:] + 147
frame #7: 0x0000000106cd346c CoreData`_PFFaultHandlerLookupRow + 588
frame #8: 0x0000000106cd2ddf CoreData`_PF_FulfillDeferredFault + 239
frame #9: 0x0000000106cd2be7 CoreData`_sharedIMPL_pvfk_core + 103
frame #10: 0x0000000103d53cff DisneyWaitTimes`AppDelegate.finishedLoadingForPark(aPark=0x00006000037cf2a0, dataType=4, error=nil, self=0x0000600000102780) at AppDelegate.swift:321
frame #11: 0x0000000103d54387 DisneyWaitTimes`@objc AppDelegate.finishedLoadingForPark(_:dataType:error:) at <compiler-generated>:0
frame #12: 0x0000000104dea869 DisneyWaitTimesKit`partial apply at <compiler-generated>:0
frame #13: 0x0000000104de9a7c DisneyWaitTimesKit`thunk for @escaping @callee_guaranteed (@unowned Park, @unowned UInt32, @unowned NSError?) -> () at <compiler-generated>:0
frame #14: 0x0000000104dea8d1 DisneyWaitTimesKit`partial apply for thunk for @escaping @callee_guaranteed (@unowned Park, @unowned UInt32, @unowned NSError?) -> () at <compiler-generated>:0
frame #15: 0x0000000104de99f4 DisneyWaitTimesKit`DisneyWaitTimesData.finishedLoadingForPark(park=0x00006000037cf2a0, dataType=4, error=nil, self=0x0000600001439b60) at DisneyWaitTimesData.swift:482
frame #16: 0x0000000104de89fa DisneyWaitTimesKit`closure #2 in closure #1 in closure #1 in DisneyWaitTimesData.loadRefurbishments(completionHandler=0x0000000104dd1980 DisneyWaitTimesKit`partial apply forwarder for closure #1 (Swift.Optional<Swift.Error>) -> () in DisneyWaitTimesKit.DataAccess.loadAllRefurbishments(Swift.Optional<(Swift.Optional<Swift.Error>) -> ()>) -> () at <compiler-generated>, self=0x0000600001439b60, request=refurbishments, context=0x0000600002b7def0, park=0x00006000037d5400) at DisneyWaitTimesData.swift:430
frame #17: 0x0000000104deb26f DisneyWaitTimesKit`partial apply for closure #2 in closure #1 in closure #1 in DisneyWaitTimesData.loadRefurbishments(_:completionHandler:) at <compiler-generated>:0
frame #18: 0x0000000104dcc0ad DisneyWaitTimesKit`thunk for @escaping @callee_guaranteed () -> () at <compiler-generated>:0
frame #19: 0x00000001087b668d libdispatch.dylib`_dispatch_call_block_and_release + 12
frame #20: 0x00000001087b76fa libdispatch.dylib`_dispatch_client_callout + 8
frame #21: 0x00000001087c49d1 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 1541
frame #22: 0x00000001072d3079 CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
frame #23: 0x00000001072cd706 CoreFoundation`__CFRunLoopRun + 2342
frame #24: 0x00000001072ccaa1 CoreFoundation`CFRunLoopRunSpecific + 625
frame #25: 0x000000010d3d31dd GraphicsServices`GSEventRunModal + 62
frame #26: 0x000000010f7b6a4f UIKitCore`UIApplicationMain + 140
frame #27: 0x0000000103d55594 DisneyWaitTimes`main at AppDelegate.swift:28
frame #28: 0x000000010882cced libdyld.dylib`start + 1
frame #29: 0x000000010882cced libdyld.dylib`start + 1