Invalid access to memory

<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

Error message:
Invalid access to memory.

Stack trace:
(00062496) ntdll.dll
(0000F13E) ntdll.dll.KiUserExceptionDispatcher
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C) System::Classes::_18201
(0037264C)%2

Status: all_insignificant

The problem happens rarely. I cannot reproduce it.

<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

Error message:
Control 'MainMessage' has no parent window

Stack trace:
(0024868E)
(002467FF)
(001F131D)
(001B17BB)
(001B19EC)
(0024980C)
(0024764D)
(002480B7)
(007D9CCA)
(007DBE15)
(000C4FF7)
(000C5864)
(000C5A36)
(000C752C)
(000994AE)
(0008C824)
(0076F068)
(00212646)
(0037264C)
(0002C2B1) USER32.dll
(0000D885) USER32.dll
(0000D1DF) USER32.dll
(0000CF9B) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.