Virheellinen muistiviittaus - Vcl::Forms::TCustomForm::CMActionUpdate

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WinSCP 5.21.6

Error message:
Virheellinen muistiviittaus.

Pinon jäljitys:
(000DF04C)WinSCP.exe
(000878AF) ntdll.dll
(00073EE1) ntdll.dll.KiUserExceptionDispatcher
(002418D8) Vcl::Forms::TCustomForm::CMActionUpdate
(00E56258) TMessageForm::Dispatch
(00282491) Vcl::Controls::TWinControl::WndProc
(0023C958) Vcl::Forms::TCustomForm::WndProc

The problem happens rarely. I cannot reproduce it.