Thanks for your report.
I have sent you an email with a debug version of WinSCP to the address you have used to register on this forum.

<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 5.9.3

Error message:
Invalid access to memory.

Stack trace:
(00467070) Tbxlists::TTBXCustomList::TTBXCustomList
(000624F6) ntdll.dll
(0000F13E) ntdll.dll.KiUserExceptionDispatcher
(00363501) System::Classes::_17670
(0036372C) System::Classes::TReader::ReadComponent
(003639DD) System::Classes::TReader::ReadDataInner
(0036394B) System::Classes::TReader::ReadData
(0037150D) System::Classes::TComponent::ReadState
(003639DD) System::Classes::TReader::ReadDataInner
(0036391C) System::Classes::TReader::ReadData
(0037150D) System::Classes::TComponent::ReadState
(0035E7C2) System::Classes::TStream::ReadComponent
(00354207) System::Classes::_17089
(00355B5B) System::Classes::_17116
(00355BE9) System::Classes::InitInheritedComponent
(00372B14) System::Classes::TDataModule::TDataModule
(0003161A) TNonVisualDataModule::TNonVisualDataModule
(000D6404) Execute
(000024A8) wWinMain
(00864459) C4941_0
(00038900) ntdll.dll
(000388D0) ntdll.dll

(00467070) Tbxlists::TTBXCustomList::TTBXCustomList
(000624F6) ntdll.dll
(0000F13E) ntdll.dll.KiUserExceptionDispatcher
(00363501) System::Classes::_17670
(0036372C) System::Classes::TReader::ReadComponent
(003639DD) System::Classes::TReader::ReadDataInner
(0036394B) System::Classes::TReader::ReadData
(0037150D) System::Classes::TComponent::ReadState
(003639DD) System::Classes::TReader::ReadDataInner
(0036391C) System::Classes::TReader::ReadData
(0037150D%2

I know how to reproduce the problem or the problem happens frequently enough. I wish to be contacted by the WinSCP team to help resolving the problem.