<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 5.9.2

Error message:
Invalid access to memory.

Stack trace:
(0032E55A) System::Variants::VarArrayGet
(0003EE3E) ntdll.dll.ZwWow64CallFunction64
(0003F5BA) ntdll.dll.KiUserExceptionDispatcher
(003227E6) System::Internal::Varhlpr::VariantGetElement
(00738310) TSFTPFileSystem::RemoveReservation
(0073A1FA) TSFTPFileSystem::UnreserveResponse
(007346EB) TSFTPFileSystem::~TSFTPFileSystem
(0076C22F) TTerminal::~TTerminal
(0008A4C6) TManagedTerminal::~TManagedTerminal
(0008B860) TTerminalManager::FreeTerminal
(0008AF2F) TTerminalManager::FreeActiveTerminal
(0001CB64) TCustomScpExplorerForm::ShowExtendedException
(0008CC4D) TTerminalManager::TerminalShowExtendedException
(007706B4) TTerminal::ShowExtendedException
(00212B5A) Vcl::Forms::TApplication::HandleException
(0042C43B) Dragdrop::TDragDrop::WndMethod
(00372BEC) System::Classes::_18201
(00007E6F) USER32.DLL.CallNextHookEx
(000080CC) USER32.DLL
(0000966A) USER32.DLL
(000096DB) USER32.DLL.DispatchMessageW

The problem happens rarely. I cannot reproduce it.