iOS / CALayerInvalidGeometry Trace when scrolling

I have the following error happening randomly but quite often when an action is fired at some point of the scroll :

CALayerInvalidGeometry Trace: <redacted> <redacted> <redacted> <redacted> <redacted> <redacted> <redacted> -[Show scrollViewWillEndDragging:withVeloci...

And, to be more accurate :

Incident Identifier: 4FE03135-D442-4CEA-B230-8322647262EE
CrashReporter Key:   6f005b28e796b18f3ab2687bb364b2be1eb137cd
Hardware Model:      iPhone5,2
Process:         etapes [2916]
Path:            /var/mobile/Applications/BF2F1016-8C00-40A3-BB75-0933F53741F0/******.app/****
Version:         ??? (???)
Code Type:       ARM (Native)
Parent Process:  launchd [1]

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00000064
Crashed Thread:  0

Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   UIKit                             0x33df7b06 -[UIView(CALayerDelegate) actionForLayer:forKey:] + 138
1   QuartzCore                        0x33ba7786 -[CALayer actionForKey:] + 70
2   QuartzCore                        0x33ba7732 _ZL12actionForKeyP7CALayerPN2CA11TransactionEP8NSString + 54
3   QuartzCore                        0x33ba7626 CA::Layer::begin_change(CA::Transaction*, unsigned int, objc_object*&) + 126
4   QuartzCore                        0x33ba2322 CA::Layer::setter(unsigned int, _CAValueType, void const*) + 178
5   QuartzCore                        0x33bce782 -[CALayer setBackgroundColor:] + 30
6   UIKit                             0x33e0ef50 -[UIView(Internal) _setBackgroundCGColor:withSystemColorName:] + 1016
7   etapes                            0x000fc8d2 0xdd000 + 129234
8   etapes                            0x000f8c6a 0xdd000 + 113770
9   CoreFoundation                    0x31fe9ad0 __invoking___ + 64
10  CoreFoundation                    0x31f4128a -[NSInvocation invoke] + 286
11  Foundation                        0x328eaf60 -[NSInvocationOperation main] + 108
12  Foundation                        0x32874a84 -[__NSOperationInternal start] + 836
13  Foundation                        0x328ecfe2 __block_global_6 + 98
14  libdispatch.dylib                 0x3a0f1790 _dispatch_call_block_and_release + 8
15  libdispatch.dylib                 0x3a0f15d8 _dispatch_client_callout + 20
16  libdispatch.dylib                 0x3a0f4e40 _dispatch_main_queue_callback_4CF + 224
17  CoreFoundation                    0x31fba1ac __CFRunLoopRun + 1284
18  CoreFoundation                    0x31f2d238 CFRunLoopRunSpecific + 352
19  CoreFoundation                    0x31f2d0c4 CFRunLoopRunInMode + 100
20  GraphicsServices                  0x35b0b336 GSEventRunModal + 70
21  UIKit                             0x33e492b4 UIApplicationMain + 1116
22  etapes                            0x000df15e 0xdd000 + 8542
23  etapes                            0x000df114 0xdd000 + 8468

I have problem to understand this error, hence to correct it. Thanks for any experienced ios dev fedback on this one