Vungle causes crashes on our released App, crash stack attached, currently Vungle is disabled

The below crash affects 4% of our users, mainly with iOS 8.3.

when we disable vungle video from dashboard, crash disappeared.

We couldn’t reproduce the crash ourselves, but we track it by Crashlytics.

Vungle Thread call stack on crash:

0 libsystem_kernel.dylib semaphore_wait_trap + 8

1 libdispatch.dylib _dispatch_semaphore_wait_slow + 256

2 CFNetwork CFURLConnectionSendSynchronousRequest + 288

3 CFNetwork +[NSURLConnection sendSynchronousRequest:returningResponse:error:] + 120

4 CrossWords -[VungleNetworkRequest execute] + 2744

5 libdispatch.dylib _dispatch_call_block_and_release + 24

6 libdispatch.dylib _dispatch_client_callout + 16

7 libdispatch.dylib _dispatch_root_queue_drain + 1848

8 libdispatch.dylib _dispatch_worker_thread3 + 108

9 libsystem_pthread.dylib _pthread_wqthread + 816

and here main thread stack:

0 Crashed: com.apple.main-thread EXC_BAD_ACCESS KERN_INVALID_ADDRESS at 0x0000000000000001

0 libGPUSupportMercury.dylib gpus_ReturnNotPermittedKillClient + 12

1 libGPUSupportMercury.dylib gpusSubmitDataBuffers + 172

2 GLEngine glFinish_Exec + 132

3 GLKit -[GLKView _display:] + 200

4 GLKit -[GLKViewController _updateAndDraw] + 552

5 QuartzCore CA::Display::DisplayLinkItem::dispatch() + 32

6 QuartzCore CA::Display::DisplayLink::dispatch_items(unsigned long long, unsigned long long, unsigned long long) + 324

7 IOKit IODispatchCalloutFromCFMessage + 376

8 CoreFoundation __CFMachPortPerform + 180

9 CoreFoundation __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 56

10 CoreFoundation __CFRunLoopDoSource1 + 436

11 CoreFoundation __CFRunLoopRun + 1640

12 CoreFoundation CFRunLoopRunSpecific + 396

13 GraphicsServices GSEventRunModal + 168

14 UIKit UIApplicationMain + 1488

15 CrossWords main.mm line 15  main

16 libdyld.dylib start + 4

please Help ASAP.

Thanks