<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 5.17.9

Error message:
External exception C0000006

Stack trace:
(003EEF60) SHELL32.dll
(000861AF) ntdll.dll
(00072B31) ntdll.dll.KiUserExceptionDispatcher
(00011011) DUser.dll
(000099E6) DUser.dll
(000098C1) DUser.dll
(00009801) DUser.dll
(00008422) DUser.dll
(00010CC2) DUser.dll
(00011A92) DUser.dll
(000116F2) DUser.dll
(0003DF59) USER32.dll
(00034ED5) USER32.dll
(00032C45) USER32.dll
(00036E43) USER32.dll.IsDialogMessageW
(00021899) USER32.dll.DialogBoxIndirectParamAorW
(0002174F) USER32.dll.DialogBoxIndirectParamAorW
(0002166D) USER32.dll.DialogBoxIndirectParamAorW
(00021626) USER32.dll.DialogBoxIndirectParamW
(00042CF4) COMDLG32.DLL
(00011313)COMDLG32.DLL
(0025FC93) Vcl::Dialogs::TCustomFileDialog::Execute
(0025CF79) Vcl::Dialogs::_16518
(0025DC16) Vcl::Dialogs::TOpenDialog::DoExecute
(0025DACB) Vcl::Dialogs::TOpenDialog::Execute
(00422C15) Comboedit::TCustomComboEdit::EditButtonClick
(0027ACF1) Vcl::Controls::TWinControl::WndProc
(001E2E80) Vcl::Stdctrls::TButtonControl::WndProc
(0027AE57) Vcl::Controls::_17076
(0027ACF1) Vcl::Controls::TWinControl::WndProc
(0027A338) Vcl::Controls::TWinControl::MainWndProc
(003A5954) System::Classes::_18201
(0003DF59) USER32.dll
(00034ED5) USER32.dll
(00034AD5) USER32.dll
(0003869D) USER32.dll
(00072AEB) ntdll.dll.KiUserCallbackDispatcher
(000328FA) USER32.dll.SendMessageW
(00035DA2) COMCTL32.DLL
(000759CE) COMCTL32.DLL
(0003DF59) USER32.dll
(00034ED5) USER32.dll
(000345B2) USER32.dll
(00032756) USER32.dll.CallWindowProcW
(0027AE02) Vcl::Controls::TWinControl::DefaultHandler
(0027ACF1) Vcl::Controls::TWinControl::WndProc
(001E2E80) Vcl::Stdctrls::TButtonControl::WndProc
(003A5954) System::Classes::_18201
(0003DF59) USER32.dll
(00034ED5) USER32.dll
(00032C45) USER32.dll
(00032A0B) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.