<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 5.9.1

Error message:
Zugriffsverletzung - ungültiger Zugriff auf den Speicher.

Stack trace:
(0070595C) TSessionData::IsSame
(00862736) C5073_3
(0086479E) ____ExceptionHandler
(00861558) __ExceptionHandler
(00081D3F) ntdll.dll
(0006F8EA) ntdll.dll.KiUserExceptionDispatcher
(00723F01) TStoredSessionList::UpdateStaticUsage
(00672175) TConfiguration::UpdateStaticUsage
(00068D71) TGUIConfiguration::UpdateStaticUsage
(000B52A6) TWinConfiguration::UpdateStaticUsage
(000D29EB) UpdateStaticUsage
(000D55AF) Execute
(000024A8) wWinMain
(0086076D) __wstartup
(0005FFD7) ntdll.dll
(0005FF9F) ntdll.dll

The problem happens rarely. I cannot reproduce it.