This is a regular commandlet crash that has occurred since at least 4.15.
Source Context
543 IFileManager::Get().SetTimeStamp(*Filename, FinalTimeStamp); 544 } 545 } 546 else 547 { 548 UE_LOG(LogSavePackage, Fatal, TEXT("Could not save to %s!"), *TempFilename); 549 } 550 } 551 else 552 { 553 UE_LOG(LogSavePackage, Fatal, TEXT("Could not write to %s!"), *TempFilename); 554 } 555 } 556 { 557 ***** FArchive* Ar = IFileManager::Get().CreateFileWriter(*TempFilenameExports); 558 if (Ar) 559 { 560 Ar->Serialize(Data.Get() + HeaderSize, DataSize - HeaderSize); 561 delete Ar; 562 Ar = nullptr;
repro steps currently unknown, occur during cooking
UE4Editor_CoreUObject!`AsyncWriteFileWithSplitExports'::`2'::FAsyncWriteWorkerWithSplitExports::DoWork() [savepackage.cpp:563] UE4Editor_CoreUObject!FAutoDeleteAsyncTask<`AsyncWriteFileWithSplitExports'::`2'::FAsyncWriteWorkerWithSplitExports>::DoWork() [asyncwork.h:95] UE4Editor_Core!FQueuedThread::Run() [threadingbase.cpp:442] UE4Editor_Core!FRunnableThreadWin::Run() [windowsrunnablethread.cpp:76]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-48654 in the post.