Invalid access to memory - TSynchronizeProgress::GetProcessed

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WinSCP 5.15.1

Error message:
Invalid access to memory.

Stack trace:
(0075F640) TSynchronizeProgress::GetProcessed
(0006248E) ntdll.dll
(0000F15E) ntdll.dll.KiUserExceptionDispatcher
(0075F697) TSynchronizeProgress::Progress
(008A4608) TProgressForm::UpdateControls
(008A513C) TProgressForm::UpdateTimerTimer
(003A346C) System::Classes::_18201
(000152F7) USER32.dll
(00015D35) USER32.dll
(00015DE3) USER32.dll
(00015E41) USER32.dll
(0000F137) ntdll.dll.KiUserCallbackDispatcher
(00015A87) USER32.dll
(00016742) UXTHEME.DLL
(0001908D) UXTHEME.DLL
(0000FB0A)UXTHEME.DLL
(0000FB91)UXTHEME.DLL
(00016294) USER32.dll
(000152F7) USER32.dll
(00015D35) USER32.dll
(0001FD3A) USER32.dll
(0001FD60) USER32.dll.CallWindowProcW
(0027891A) Vcl::Controls::TWinControl::DefaultHandler
(002360B5) Vcl::Forms::TCustomForm::WMSysCommand
(00278809) Vcl::Controls::TWinControl::WndProc
(00232CD0) Vcl::Forms::TCustomForm::WndProc

The problem happens rarely. I cannot reproduce it.