[AVSampleBufferDisplayLayer enqueueSampleBuffer:] crash when locking the screen

I use VTDecompressionSessionDecodeFrame to decode nalu and render pixelbuffer by AVSampleBufferDisplayLayer. Crash happened twice when I lock the screen which is rendering pixelbuffer. Did anyone ever suffer from this and solve it? Great thanks for help!

crash log:

Date/Time: 2016-07-07 10:55:42.515 +0800
Launch Time: 2016-07-07 10:39:13.926 +0800
OS Version: iOS 8.4 (12H143) 
Report Version: 105
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x00000001f9c1beb8
Triggered by Thread: 23

Thread 23 Crashed:
0 libobjc.A.dylib               0x0000000194e6fbd0 objc_msgSend + 16 
1 AVFoundation                  0x0000000181a4aa94 - [AVSampleBufferDisplayLayer dealloc] + 444 
2 QuartzCore                    0x0000000187537c50 CA::Layer::free_transaction(CA::Transaction*) + 180 
3 QuartzCore                    0x0000000187533c58 CA::Transaction::commit() + 656 
4 MediaToolbox                  0x000000018572055c FigLayerSynchronizerSynchronizeToMoment + 1480 
5 MediaToolbox                  0x0000000185917870 videoQueueRemote_SynchronizeLayerToMoment + 68 
6 MediaToolbox                  0x00000001856c3d68 FigSyncMomentSourceSetTimebase + 308 
7 MediaToolbox                  0x000000018571f890 FigSyncMomentSourceCreateWithDispatchQueue + 184 
8 MediaToolbox                  0x0000000185917000 videoQueueRemote_EnqueueFrame + 476 
9 AVFoundation                  0x0000000181a4c8fc -[AVSampleBufferDisplayLayer(AVSampleBufferDisplayLayerQueueManagement) enqueueSampleBuffer:] + 384 
10 StarMaker                    0x0000000100490718 -[FFMoviePlayerView enqueueSampleBuffer:toLayer:] (FFMoviePlayerView.m:459)
11 StarMaker                    0x0000000100490698 -[FFMoviePlayerView dispatchPixelBuffer:] (FFMoviePlayerView.m:451) 
12 StarMaker                    0x000000010048b844 HWVideoDecoder::renderBuffer() (HWVideoDecoder.cpp:193) 
13 StarMaker                    0x000000010048bbbc HWVideoDecoder::beginHWDecode(AVPacket*) (HWVideoDecoder.cpp:323)
14 StarMaker                    0x000000010048e028 MediaDecoder::run() (MediaDecoder.cpp:409) 
15 StarMaker                    0x0000000100487df4 Thread::startRoutine(void*) (Thread.cpp:157) 
16 libsystem_pthread.dylib      0x00000001956bbdc4 _pthread_body + 160 
17 libsystem_pthread.dylib      0x00000001956bbd20 _pthread_start + 156 
18 libsystem_pthread.dylib      0x00000001956b8ef4 thread_start + 0
[AVSampleBufferDisplayLayer enqueueSampleBuffer:] crash when locking the screen
 
 
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