Unity iOS unreproducable crashes in methods of ArrayList with mono_gc_out_of_memory

We have crashes in our Unity iOS app.
We cannot reproduce them when debugging, but we regularly catch this crash.

We tried to analyze crash logs. (crash log is in the bottom of the post) We examine part of code mentioned in crash log (m_Controller... methods), and cant see something that could cause crash.
We tried to imagine situations that can occurs in that part of code, but see nothing that can lead to crash. There are small* array of strings which is loadaed from disk, and modified. We thinking of rewriting this part of code, but we afraid that otherp part of program can affect and lead to this crash, and that crash will remain after rewriting.

We tried to add try-catch block in this part of code and process situation when exception occurs gracefully (move user to our app's main menu), but we have to remove this block due to requirements to our app.

Also, I think that crash occurs only (or at least much more frequent) in Ad-hoc build (which uses Release configuration in Xcode). In parts of crash logs you can see mono_gc_out_of_memory in GC_malloc, which is looking very strange to me (I thought that iOS generates memory warning when memory is low, but possibly mono has its own constraints)

Also, there is another one or two crashes in this part of code with different crash logs (without mono_gc_out_of_memory, but ), but all of them occurs in methods of ArrayList ( ArrayList.Clear() in other situations).

Can you help us with this situation? Can you give us any advice please on how should we deal with this crashes?

 Exception Type:  EXC_BREAKPOINT (SIGTRAP)
 Exception Codes: 0x0000000000000001, 0x00000000e7ffdefe
 Crashed Thread:  0
 
 Thread 0 name:  Dispatch queue: com.apple.main-thread
 Thread 0 Crashed:
 0   MyApp                           0x00f0e150 CrashedCheckBellowForHintsWhy() (CrashReporter.mm:73)
 1   MyApp                           0x00dcd888 m_wrapper_runtime_invoke_object_runtime_invoke_dynamic_intptr_intptr_intptr_intptr + 200
 2   MyApp                           0x01462eec mono_jit_runtime_invoke + 2152
 3   MyApp                           0x01504f24 mono_runtime_invoke + 132
 4   MyApp                           0x015050a8 mono_runtime_delegate_invoke + 128
 5   MyApp                           0x0150931c call_unhandled_exception_delegate + 340
 6   MyApp                           0x0150b230 mono_unhandled_exception + 328
 7   MyApp                           0x01473080 mono_handle_exception_internal + 952
 8   MyApp                           0x01473918 mono_handle_exception + 64
 9   MyApp                           0x0148f6d8 mono_arm_throw_exception + 184
 10  MyApp                           0x00e76ecc throw_exception + 44
 11  MyApp                           0x014b7f44 mono_gc_out_of_memory + 16
 12  MyApp                           0x0156a62c GC_generic_malloc + 452
 13  MyApp                           0x0156a6cc GC_malloc + 140
 14  MyApp                           0x015045fc mono_array_new_specific + 272
 15  MyApp                           0x00dd27ac m_wrapper_managed_to_native_object___icall_wrapper_mono_array_new_specific_intptr_int + 68
 16  MyApp                           0x00b7b2b8 m_System_Collections_ArrayList_InsertRange_int_System_Collections_ICollection + 212
 17  MyApp                           0x00b7b898 m_System_Collections_ArrayList_AddRange_System_Collections_ICollection + 52
 18  MyApp                           0x001fc3fc m_Controller_PrepareSkins_string_string_string_string_string_string_string__ + 1600
 19  MyApp                           0x001fda88 m_Controller_Awake + 4972