<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 5.21.5

Error message:
Invalid access to memory.

Stack trace:
(004EDA5F) Tbxstatusbars::TTBXCustomStatusBar::SetSimplePanel
(000624F6) ntdll.dll
(0000F13E) ntdll.dll.KiUserExceptionDispatcher
(0001A1FC) TCustomScpExplorerForm::Idle
(0004DDF7) TNonVisualDataModule::DoIdle
(0004DDB4) TNonVisualDataModule::SessionIdleTimerTimer
(003C9C0C) System::Classes::_18201
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167BF) USER32.dll
(00016885) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.