<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 6.5.5

Error message:
Invalid access to memory.

Stack trace:
(00D9184F) std::_Tree<std::_Tmap_traits<System::UnicodeString, Vcl::Comctrls::TListItem *, std::less<System::UnicodeString>, std::allocator<std::pair<System::UnicodeString, Vcl::Comctrls::TListItem *> >, 0> >::_Lbound
(00099A1F) ntdll.dll
(00078491) ntdll.dll.KiUserExceptionDispatcher
(00D9174F) TFileFindDialog::FileOperationFinished
(0002F97F) TCustomScpExplorerForm::DoEditFoundFiles
(00D9282E) TFileFindDialog::FileListOperation
(00D92CE0) TFileFindDialog::EditActionExecute
(003A356D) Vcl::Controls::TWinControl::WndProc
(003C7B74) Vcl::Stdctrls::TButtonControl::WndProc
(003A36C7) Vcl::Controls::_17122
(003A356D) Vcl::Controls::TWinControl::WndProc
(004A77B4) Vcl::Forms::TCustomForm::WndProc
(00E0706B) Vclcommon::C4884_0
(003A2A78) Vcl::Controls::TWinControl::MainWndProc
(00204C90) System::Classes::_18364
(000328AD) USER32.dll
(000232A1) USER32.dll
(00022D1B) USER32.dll
(0002CE8D) USER32.dll
(0007844B) ntdll.dll.KiUserCallbackDispatcher
(00039AFD) USER32.dll
(00021CD1) USER32.dll.SendMessageW
(00074D17) COMCTL32.DLL
(00083B58) COMCTL32.DLL
(000328AD) USER32.dll
(000232A1) USER32.dll
(00022B62) USER32.dll.CallWindowProcW
(003A3675) Vcl::Controls::TWinControl::DefaultHandler
(003A356D) Vcl::Controls::TWinControl::WndProc
(003C7B74) Vcl::Stdctrls::TButtonControl::WndProc
(00204C90) System::Classes::_18364
(000328AD) USER32.dll
(000232A1) USER32.dll
(00021AB3) USER32.dll
(0002161B) USER32.dll.DispatchMessageW
(0001ED8B)QIPCAP.dll

(00D92849) TFileFindDialog::FileListOperation
(00099A1F) ntdll.dll
(00078491) ntdll.dll.KiUserExceptionDispatcher
(00D92CE0) TFileFindDialog::EditActionExecute
(003A356D) Vcl::Controls::TWinControl::WndProc
(003C7B74) Vcl::Stdctrls::TButtonControl::WndProc
(003A36C7) Vcl::Controls::_17122
(003A356D) Vcl::Controls::TWinControl::WndProc
(004A77B4) Vcl::Forms::TCustomForm::WndProc
(00E0706B) Vclcommon::C4884_0
(003A2A78) Vcl::Controls::TWinControl::MainWndProc
(00204C90) System::Classes::_18364
(000328AD) USER32.dll
(000232A1) USER32.dll
(00022D1B) USER32.dll
(0002CE8D) USER32.dll
(0007844B) ntdll.dll.KiUserCallbackDispatcher
(00039AFD) USER32.dll
(00021CD1) USER32.dll.SendMessageW
(00074D17) COMCTL32.DLL
(00083B58) COMCTL32.DLL
(000328AD) USER32.dll
(000232A1) USER32.dll
(00022B62) USER32.dll.CallWindowProcW
(003A3675) Vcl::Controls::TWinControl::DefaultHandler
(003A356D) Vcl::Controls::TWinControl::WndProc
(003C7B74) Vcl::Stdctrls::TButtonControl::WndProc
(00204C90) System::Classes::_18364
(000328AD) USER32.dll
(000232A1) USER32.dll
(00021AB3) USER32.dll
(0002161B) USER32.dll.DispatchMessageW
(0001ED8B)QIPCAP.dll

The problem happens rarely. I cannot reproduce it.