Application crashes very rarely with UI update on secondary thread

It is really very strange for me as my app is working fine at debug mode & when tried by tester with release build RARELY it gives crash. What I have understood from console log & crash log is that somewhere UI is trying to update from secondary thread but NOT always.

At crash point my console log says,

MyApp[715] <Warning>: CoreAnimation: warning, deleted thread with uncommitted CATransaction; set CA_DEBUG_TRANSACTIONS=1 in environment to log backtraces.May 21 10:51:25 
MyApp[715] <Warning>: bool _WebTryThreadLock(bool), 0x1e1dd280: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...May 21 10:51:25 
MyApp[715] <Notice>: 1   0x38b048f7 WebThreadLock

& device crash logs crash thread description & error type are as below

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0xbbadbeef 
Crashed Thread:  15 
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.
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Thread 15 Crashed: 0  
WebCore                         0x38b03944_WebTryThreadLock(bool) + 164 1  
WebCore                         0x38b048f2 WebThreadLock + 62 2  
UIKit                           0x374424f6 -[UIWebTiledView layoutSubviews] + 38 3   
UIKit                           0x374424c6 -[UIWebDocumentView layoutSubviews] + 106 4  
UIKit                           0x373bb7fe -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 254 5 
QuartzCore                      0x30e92d5e -[CALayer layoutSublayers] + 210 6  
QuartzCore                      0x30e928fc CA::Layer::layout_if_needed(CA::Transaction*) + 456 7 
QuartzCore                      0x30e93830 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 12 8  
QuartzCore                      0x30e93216 CA::Context::commit_transaction(CA::Transaction*) + 234 9   
QuartzCore                      0x30e93024 CA::Transaction::commit() + 312 10 
QuartzCore                      0x30ed9df6 CA::Transaction::release_thread(void*) + 166 11  libsystem_c.dylib               0x31150128 _pthread_tsd_cleanup + 172 12  
libsystem_c.dylib               0x3114fdfe _pthread_exit + 114 13 
libsystem_c.dylib               0x31169160 pthread_exit + 24 14 
Foundation                      0x358bf226 +[NSThread exit] + 6 15 
Foundation                      0x35936696 __NSThread__main__ + 998 16 
libsystem_c.dylib               0x3115d30e _pthread_start + 306 17 
libsystem_c.dylib               0x3115d1d4 thread_start + 4 

Thread 15 crashed with ARM Thread State (32-bit):     r0: 0xbbadbeef    r1: 0x00000000      r2: 0x030ba404      r3: 0x00000001     r4: 0x1e1dd280    r5: 0x3b4cacc0      r6: 0x00000000      r7: 0x030baa74     r8: 0x00000028    r9: 0x00006200     r10: 0x00000000     r11: 0x030bbc70     ip: 0x3b4061e0    sp: 0x030baa6c      lr: 0x38b0393b      pc: 0x38b03944   cpsr: 0x60000030

I am not very sure about this fix as i have not yet reproduced it at my end. If anyone at-least could help me out for reproducing then it would be great help :)

you do GUI changes in background thread but according to apple you are not changes in GUI in background thread...so use performSelectorOnMainThread to GUI change