VectorKit/OpenGL crashes in MKMapView since iOS 9 - ios

Question

I can see from the Crashlytics that some of my app users are getting the following crashes. I have never seen these myself and don't know how to reproduce them as they don't have my code in the stack trace. I have read about OpenGL that some crashes are possible when trying to update the surface while the app is in the background. Not sure if that is the case here because the crashes didn't occur before iOS 9.
I have several annotations on the map, custom MKAnnotationView derived views, some custom overlays and a MKTileOverlay derived tile source. The map handling code and overlays are Objective-C, but my app has also some Swift code.
Does anybody have any ideas what could be the reason for the crashes?
1)
Thread : Crashed: com.apple.maps.geogl.renderQueue
0 VectorKit 0x18c82a894 ___ZN3ggl10GLRenderer5frameEPNS_12RenderTargetEPNS_11RenderQueueE_block_invoke_2 + 876
1 VectorKit 0x18c82a47c ___ZN3ggl10GLRenderer5frameEPNS_12RenderTargetEPNS_11RenderQueueE_block_invoke + 212
2 libdispatch.dylib 0x182625630 _dispatch_call_block_and_release + 24
3 libdispatch.dylib 0x1826255f0 _dispatch_client_callout + 16
4 libdispatch.dylib 0x182631634 _dispatch_queue_drain + 864
2)
Thread : Crashed: com.apple.mapdisplay.stylesheetLoadQueue
0 libdispatch.dylib 0x183ec2a90 dispatch_async + 76
1 libdispatch.dylib 0x183ec2a88 dispatch_async + 68
2 VectorKit 0x18df501c4 std::__1::__function::__func<-[VKTileSetBackedTileSource setStyleManager:]::$_0, std::__1::allocator<-[VKTileSetBackedTileSource setStyleManager:]::$_0>, void (std::__1::shared_ptr<gss::StyleManager>, bool)>::operator()(std::__1::shared_ptr<gss::StyleManager>&&, bool&&) + 176
3 VectorKit 0x18e11533c std::__1::__function::__func<gss::StyleManager::addFinishedDecodingGlobalPropertiesCallback(std::__1::function<void (std::__1::shared_ptr<gss::StyleManager>, bool)>)::$_0, std::__1::allocator<gss::StyleManager::addFinishedDecodingGlobalPropertiesCallback(std::__1::function<void (std::__1::shared_ptr<gss::StyleManager>, bool)>)::$_0>, void (bool)>::operator()(bool&&) + 88
4 VectorKit 0x18e10c248 ___ZN3gss10StyleSheet43addFinishedDecodingGlobalPropertiesCallbackENSt3__18functionIFvbEEE_block_invoke + 56
5 libdispatch.dylib 0x183ec1630 _dispatch_call_block_and_release + 24
6 libdispatch.dylib 0x183ec15f0 _dispatch_client_callout + 16
7 libdispatch.dylib 0x183ecd634 _dispatch_queue_drain + 864
8 libdispatch.dylib 0x183ec50f4 _dispatch_queue_invoke + 464
9 libdispatch.dylib 0x183ecf504 _dispatch_root_queue_drain + 728
10 libdispatch.dylib 0x183ecf224 _dispatch_worker_thread3 + 112
11 libsystem_pthread.dylib 0x1840d5470 _pthread_wqthread + 1092
12 libsystem_pthread.dylib 0x1840d5020 start_wqthread + 4
3)
Thread : Fatal Exception: NSGenericException
0 CoreFoundation 0x23f6a2eb __exceptionPreprocess
1 libobjc.A.dylib 0x23736dff objc_exception_throw
2 CoreFoundation 0x23f69d6d -[NSException name]
3 VectorKit 0x2c923af9 -[VKRasterOverlayTileSource _queueDraw:]
4 VectorKit 0x2c5e74ad -[VKTileSource fetchTileForKey:]
5 VectorKit 0x2c7c512d -[VKTileProvider dirtyTilesFromTileSource:]
6 libdispatch.dylib 0x23b07dd7 _dispatch_call_block_and_release
7 libdispatch.dylib 0x23b07dc3 _dispatch_client_callout
8 libdispatch.dylib 0x23b0c671 _dispatch_main_queue_callback_4CF
9 CoreFoundation 0x23f2cfc5 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__
10 CoreFoundation 0x23f2b4bf __CFRunLoopRun
11 CoreFoundation 0x23e7dbb9 CFRunLoopRunSpecific
12 CoreFoundation 0x23e7d9ad CFRunLoopRunInMode
13 GraphicsServices 0x250f7af9 GSEventRunModal
14 UIKit 0x28169fb5 UIApplicationMain
15 MyApp 0x252d44 main (main.swift:12)
16 libdispatch.dylib 0x23b30873 (Missing)

Answer 1

A similar crashlog from my app as the following. From the thread name "com.apple.maps.geogl.renderQueue", I guess that is related with usage of the MapKit framework.
I found the "gpus_ReturnNotPermittedKillClient" in the Technical QA:
"How to fix OpenGL ES application crashes when moving to the background"
https://developer.apple.com/library/archive/qa/qa1766/_index.html
Crashed: com.apple.maps.geogl.renderQueue
EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000001
0 libGPUSupportMercury.dylib 0x190a45f08 gpus_ReturnNotPermittedKillClient
1 libGPUSupportMercury.dylib 0x190a46ec4 gpusSubmitDataBuffers
2 VectorKit 0x18c7d1a0c ___ZN3ggl10GLRenderer5frameEPNS_12RenderTargetEPNS_11RenderQueueE_block_invoke + 212
3 libdispatch.dylib 0x181ec94bc _dispatch_call_block_and_release + 24
4 libdispatch.dylib 0x181ec947c _dispatch_client_callout + 16
5 libdispatch.dylib 0x181ed54c0 _dispatch_queue_drain + 864
6 libdispatch.dylib 0x181eccf80 _dispatch_queue_invoke + 464
7 libdispatch.dylib 0x181ed7390 _dispatch_root_queue_drain + 728
8 libdispatch.dylib 0x181ed9934 _dispatch_worker_thread + 124
9 libsystem_pthread.dylib 0x1820e3b28 _pthread_body + 156
10 libsystem_pthread.dylib 0x1820e3a8c _pthread_body + 154
11 libsystem_pthread.dylib 0x1820e1028 thread_start + 4