An imported file that resides within the project's folders gets a relative path. That path is not updated it you copy the uasset to another folder. That breaks the Reimporting functionality.

An imported file that resides within the project's folders gets a relative path. That path is not updated it you copy the uasset to another folder, so from the location of the new asset's the relative path does not point to the source file. That breaks the Reimporting functionality. Moving the file does trigger the resolving of the relative path structure, only the Copy operation breaks it. I've added plenty of images in case the explanation is not enough.

1. On an empty project, add an importable file (for instance, a FBX file) within the project's folder structure.
2. That triggers the import functionality, import it to any folder.
3. If you check the Source File path, it's relative.
4. Drag'n'Drop the file to another folder, choose Copy.
5. The new file will keep the relative path as the original. That's the issue, the path is wrong and the Reimporting will stop working automatically.
6. If you Move instead, it does trigger the retargeting of the relative path.

This callstack is not a crash, but this handles the copy operation.

> UnrealEditor-ContentBrowser.dll!R<lambda_2>@?BB@?R<lambda_1>@?O@HandleDragDropOnItem@DragDropHandler@@YA_NAEBUFContentBrowserItem@@AEBVFDragDropEvent@@AEBV?$TSharedRef@VSWidget@@$00@@@Z@QEBA@AEAUFToolMenuSection@@@Z@QEBA@XZ() Line 310 C++ [Inline Frame] UnrealEditor-ContentBrowser.dll!Invoke(DragDropHandler::HandleDragDropOnItem::_l14::<lambda_1>:[Image Removed])::l17::<lambda_2> &) Line 47 C++ [Inline Frame] UnrealEditor-ContentBrowser.dll!UE::Core::Private::Tuple::TTupleBase<TIntegerSequence<unsigned int>>::ApplyAfter(DragDropHandler::HandleDragDropOnItem::l14::<lambda_1>:[Image Removed])::l17::<lambda_2> &) Line 309 C++ UnrealEditor-ContentBrowser.dll!?ExecuteIfSafe@?$TBaseFunctorDelegateInstance@$$A6AXXZUFDefaultDelegateUserPolicy@@V<lambda_2>@?BB@?R<lambda_1>@?O@HandleDragDropOnItem@DragDropHandler@@YA_NAEBUFContentBrowserItem@@AEBVFDragDropEvent@@AEBV?$TSharedRef@VSWidget@@$00@@@Z@QEBA@AEAUFToolMenuSection@@@Z@$$V@@UEBA_NXZ() Line 870 C++ [Inline Frame] UnrealEditor-Slate.dll!TDelegate<void __cdecl(void),FDefaultDelegateUserPolicy>::ExecuteIfBound() Line 570 C++ UnrealEditor-Slate.dll!FUIAction::Execute() Line 139 C++ UnrealEditor-Slate.dll!SMenuEntryBlock::OnClicked(bool bCheckBoxClicked) Line 1167 C++ UnrealEditor-Slate.dll!SMenuEntryBlock::OnMenuItemButtonClicked() Line 1118 C++ [Inline Frame] UnrealEditor-Slate.dll!Invoke(FReply(SMenuEntryBlock::)()) Line 66 C++ [Inline Frame] UnrealEditor-Slate.dll!UE::Core::Private::Tuple::TTupleBase<TIntegerSequence<unsigned int>>::ApplyAfter(FReply(SMenuEntryBlock::)() &) Line 309 C++ UnrealEditor-Slate.dll!V::TBaseSPMethodDelegateInstance::Execute() Line 281 C++ [Inline Frame] UnrealEditor-Slate.dll!TDelegate<FReply __cdecl(void),FDefaultDelegateUserPolicy>::Execute() Line 549 C++ UnrealEditor-Slate.dll!SButton::ExecuteOnClick() Line 465 C++ UnrealEditor-Slate.dll!SButton::OnMouseButtonUp(const FGeometry & MyGeometry, const FPointerEvent & MouseEvent) Line 390 C++ UnrealEditor-Slate.dll!SMenuEntryButton::OnMouseButtonUp(const FGeometry & MyGeometry, const FPointerEvent & MouseEvent) Line 434 C++ [Inline Frame] UnrealEditor-Slate.dll!FSlateApplication::RoutePointerUpEvent::l8::<lambda_2>::operator()(const FArrangedWidget &) Line 5293 C++ UnrealEditor-Slate.dll!$Route@VFReply@@VFToLeafmostPolicy@FEventRouter@@UFPointerEvent@@V<lambda_2>@?7??RoutePointerUpEvent@FSlateApplication@@QEAA?AV1@AEBVFWidgetPath@@AEBU4@@Z@@FEventRouter@@SA?AVFReply@@PEAVFSlateApplication@@VFToLeafmostPolicy@0@UFPointerEvent@@AEBV<lambda_2>@?7??RoutePointerUpEvent@2@QEAA?AV1@AEBVFWidgetPath@@AEBU4@@Z@W4ESlateDebuggingInputEvent@@@Z(FSlateApplication * ThisApplication, FEventRouter::FToLeafmostPolicy RoutingPolicy, FPointerEvent EventCopy, const FSlateApplication::RoutePointerUpEvent::l8::<lambda_2> & Lambda, ESlateDebuggingInputEvent DebuggingInputEvent) Line 442 C++ UnrealEditor-Slate.dll!FSlateApplication::RoutePointerUpEvent(const FWidgetPath & WidgetsUnderPointer, const FPointerEvent & PointerEvent) Line 5279 C++ UnrealEditor-Slate.dll!FSlateApplication::ProcessMouseButtonUpEvent(const FPointerEvent & MouseEvent) Line 5857 C++ UnrealEditor-Slate.dll!FSlateApplication::OnMouseUp(const EMouseButtons::Type Button, const UE::Math::TVector2<double> CursorPos) Line 5813 C++ UnrealEditor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage(const FDeferredWindowsMessage & DeferredMessage) Line 2243 C++ UnrealEditor-ApplicationCore.dll!FWindowsApplication::DeferMessage(TSharedPtr<FWindowsWindow,1> & NativeWindow, HWND_ * InHWnd, unsigned int InMessage, unsigned _int64 InWParam, __int64 InLParam, int MouseX, int MouseY, unsigned int RawInputFlags) Line 2750 C++ UnrealEditor-ApplicationCore.dll!FWindowsApplication::ProcessMessage(HWND_ * hwnd, unsigned int msg, unsigned _int64 wParam, __int64 lParam) Line 1919 C++ [Inline Frame] UnrealEditor-ApplicationCore.dll!WindowsApplication_WndProc(HWND_ *) Line 923 C++ UnrealEditor-ApplicationCore.dll!FWindowsApplication::AppWndProc(HWND__ * hwnd, unsigned int msg, unsigned _int64 wParam, __int64 lParam) Line 929 C++ [External Code] [Inline Frame] UnrealEditor-ApplicationCore.dll!WinPumpMessages() Line 116 C++ UnrealEditor-ApplicationCore.dll!FWindowsPlatformApplicationMisc::PumpMessages(bool bFromMainLoop) Line 145 C++ UnrealEditor.exe!FEngineLoop::Tick() Line 5850 C++ [Inline Frame] UnrealEditor.exe!EngineTick() Line 61 C++ UnrealEditor.exe!GuardedMain(const wchar_t * CmdLine) Line 180 C++ UnrealEditor.exe!LaunchWindowsStartup(HINSTANCE_ * hInInstance, HINSTANCE__ * hPrevInstance, char * _formal, int nCmdShow, const wchar_t * CmdLine) Line 247 C++ UnrealEditor.exe!WinMain(HINSTANCE_ * hInInstance, HINSTANCE__ * hPrevInstance, char * pCmdLine, int nCmdShow) Line 298 C++ [External Code]