Unity iOS crash in Mutex.cpp - Line 64

Hello,

Code (CSharp):

1. Crashed: Thread
2. 0  OurGame                            0x106247010 il2cpp::os::FastMutex::Lock() + 64 (Mutex.cpp:64)
3. 1  OurGame                            0x10623d620 il2cpp::icalls::mscorlib::System::Threading::Thread::SetState(Il2CppThread*, unsigned int) + 112 (Thread.cpp:112)
4. 2  OurGame                            0x10623d680 il2cpp::icalls::mscorlib::System::Threading::Thread::Sleep_internal(int) + 119 (Thread.cpp:119)
5. 3  OurGame                            0x10950675c GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4385269596
6. 4  OurGame                            0x1094ecad8 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4385163992
7. 5  OurGame                            0x109742250 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4387611216
8. 6  OurGame                            0x109742304 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4387611396
9. 7  OurGame                            0x109507f84 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4385275780
10. 8  OurGame                            0x109507cfc GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4385275132
11. 9  OurGame                            0x10b0d5944 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4414429508
12. 10 OurGame                            0x10b0d8340 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4414440256
13. 11 OurGame                            0x10b0d7e94 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4414439060
14. 12 OurGame                            0x10b0d0df8 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4414410232
15. 13 OurGame                            0x10950826c GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4385276524
16. 14 OurGame                            0x109507f84 GMSx_absl::base_internal::MallocHook::InvokePreSbrkHookSlow(long) + 4385275780
17. 15 OurGame                            0x10491f5ac RuntimeInvoker_TrueVoid_t22962CB4C05B1D89B55A6E1139F0E87A90987017(void (*)(), MethodInfo const*, void*, void**) + 74265 (Il2CppInvokerTable.cpp:74265)
18. 16 OurGame                            0x106270ae0 il2cpp::vm::Runtime::Invoke(MethodInfo const*, void*, void**, Il2CppException**) + 550 (Runtime.cpp:550)
19. 17 OurGame                            0x10623d8b8 il2cpp::icalls::mscorlib::System::Threading::ThreadStart(void*) + 159 (Thread.cpp:159)
20. 18 OurGame                            0x106246a9c il2cpp::os::Thread::RunWrapper(void*) + 176 (Thread.cpp:176)
21. 19 OurGame                            0x106248e28 il2cpp::os::ThreadImpl::ThreadStartWrapper(void*) + 107 (ThreadImpl.cpp:107)
22. 20 libsystem_pthread.dylib        0x1e01efcb0 _pthread_start + 320
23. 21 libsystem_pthread.dylib        0x1e01f8778 thread_start + 8

This is the crash we are facing in-store build, I have shared the crash thread stack trace from the firebase Crashlytics dashboard. we are using unity 2019.2.14f1.
The issue is appearing only for iOS users and also when it happened 85% of the time app was in the background state. 99% of the affected devices are iPhones and it happens in all the iOS versions i.e 12,13 and 14.

So can someone tell me what is going on here? and also how we can track this iL2cpp stack trace backward so that we can point out our C# code?

We have couple of other crashes as well but unique thing is in all the crash stack traces I'm able to see this particular line

Code (CSharp):

1. RuntimeInvoker_TrueVoid_t22962CB4C05B1D89B55A6E1139F0E87A90987017(void (*)(), MethodInfo const*, void*, void**) + 74265 (Il2CppInvokerTable.cpp:74265)

It looks like some exception handler but not sure what is happening here.