Invalid access to memory - @Tb2dock@TTBCustomDockableWindow@WMNCPaint$qqrr24Winapi@Messages@TMessage

Hello

I was using WinSCP then locked my laptop. That message appeared when I unlocked my laptop.

WinSCP 6.3.6

Error message:
Invalid access to memory.

Stack trace:
(00476517)
(000B042F) ntdll.dll
(0007AABA) ntdll.dll.KiUserExceptionDispatcher
(004D305F) @Tb2dock@TTBCustomDockableWindow@WMNCPaint$qqrr24Winapi@Messages@TMessage
(00409029)
(00408670)
(00226F74)
(00036941) USER32.dll
(00025018) USER32.dll
(00024ABB) USER32.dll
(00031347) USER32.dll
(0007AA94) ntdll.dll.KiUserCallbackDispatcher
(004FFCAE)
(00511854)
(00036941) USER32.dll
(00025018) USER32.dll
(00024ABB) USER32.dll
(00035334) USER32.dll
(0007AA94) ntdll.dll.KiUserCallbackDispatcher
(0003032C) USER32.dll.PeekMessageW
(003CCB10)
(00D098CE)
(00D0933E)
(0001B0DD)
(00012BD7)
(00012DE4)
(00012FA3)
(0004F16F)
(00275814)
(003595F5)
(00226F74)
(00036941) USER32.dll
(00025018) USER32.dll
(000244A5) USER32.dll
(0002400B) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.