Invalid access to memory - TFileFindDialog::FocusFile

<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 5.13.3

Error message:
Invalid access to memory.

Stack trace:
(00803886) TFileFindDialog::FocusFile
(0003140E) ntdll.dll.RtlRaiseStatus
(0002F1C6) ntdll.dll.KiUserExceptionDispatcher
(0080393C) TFileFindDialog::FocusActionExecute
(0025B025) Vcl::Controls::TWinControl::WndProc
(001C31B4) Vcl::Stdctrls::TButtonControl::WndProc
(0025B18B) Vcl::Controls::_17076
(0025B025) Vcl::Controls::TWinControl::WndProc
(002154EC) Vcl::Forms::TCustomForm::WndProc

The problem happens rarely. I cannot reproduce it.

I've left a SFTP session open for one of my servers and a "Search" window open too for a while. I've pressed the "Locate" o "Buscar" button and that error appear. Restarting the WinSCP software again fixed the problem.

WinSCP 6.3.1

Error message:
Acceso a memoria no válido

Rastreo de la pila:
(00CBAA8A) TFileFindDialog::FocusFile
(0009812F) ntdll.dll
(00077D31) ntdll.dll.KiUserExceptionDispatcher
(00CBAB40) TFileFindDialog::FocusActionExecute
(00408A39) Vcl::Controls::TWinControl::WndProc
(00370C48) Vcl::Stdctrls::TButtonControl::WndProc
(00408B9F) Vcl::Controls::_17076
(00408A39) Vcl::Controls::TWinControl::WndProc
(003C2F48) Vcl::Forms::TCustomForm::WndProc

The problem happens rarely. I cannot reproduce it.