Why Does SceneManager.LoadSceneAsync crash on startup on Android 11?

Hi We are seeing some weird behaviour on android 11 devices. They are crashing around 10% of the time we start our app, with the following crash report:

 Native StackTrace:

 Thread 0 (crashed)
 0   libunity.so                        0x000000771bfdc770 bool UnityDefaultAllocator<LowLevelAllocator>::AllocationPage<(RequestType)0>(void const*) const 
 1   libunity.so                        0x000000771bfdc310 UnityDefaultAllocator<LowLevelAllocator>::RegisterAllocation(void const*) 
 2   libunity.so                        0x000000771bfdc260 UnityDefaultAllocator<LowLevelAllocator>::Allocate(unsigned long, int) 
 3   libunity.so                        0x000000771bb5fccc MemoryManager::Allocate(unsigned long, unsigned long, MemLabelId, AllocateOptions, char const*, int) 
 4   libunity.so                        0x000000771bc5b694 dynamic_array_detail::dynamic_array_data::resize_buffer(unsigned long, ResizePolicy, unsigned long, unsigned long) 
 5   libunity.so                        0x000000771bbc95cc SharedTextureData::SharedTextureData(MemLabelId, int, int, TextureFormat, unsigned long, int, int, bool, bool) 
 6   libunity.so                        0x000000771bb9f974 Texture2D::CreatePixelDataWhenReading(unsigned int, bool) 
 7   libunity.so                        0x000000771bba0fa4 void Texture2D::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) 
 8   libunity.so                        0x000000771bcd75b8 SerializedFile::ReadObject(long, ObjectCreationMode, bool, TypeTree const**, bool*, Object&) 
 9   libunity.so                        0x000000771bccee54 PersistentManager::ReadAndActivateObjectThreaded(int, SerializedObjectIdentifier const&, SerializedFile*, bool, bool, PersistentManager::LockFlags) 
 10  libunity.so                        0x000000771bccf434 PersistentManager::LoadFileCompletelyThreaded(core::basic_string<char, core::StringStorageDefault<char> > const&, long*, int*, int, PersistentManager::LoadFlags, LoadProgress&, PersistentManager::LockFlags) 
 11  libunity.so                        0x000000771bc1260c LoadSceneOperation::Perform() 
 12  libunity.so                        0x000000771bc13f60 PreloadManager::ProcessSingleOperation() 
 13  libunity.so                        0x000000771bc13dac PreloadManager::Run() 
 14  libunity.so                        0x000000771bc13d18 PreloadManager::Run(void*) 
 15  libunity.so                        0x000000771bc6ac7c Thread::RunThreadWrapper(void*) 
 16  libc.so                            0x0000007a321b1888 <system symbols missing> 
 17  libc.so                            0x0000007a32151e08 <system symbols missing> 

It is happening when we are trying to load our main scene during startup:

 Debug.Log("Loading " + sceneName );
 SceneManager.LoadSceneAsync(sceneName);

We are seeing this across all the Android 11 devices we can test, mostly Google Pixel Phones. we have tried both 2019.4.10f1 and 2019.4.11f1 also with the lates version of unity ads in both cases with same results.

Does anyone have any pointers to what goes wrong?

Thanks Simon