<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
This bug is reproducible but I do not need help resolving it, this is just FYI. This is a pretty weird case, and it just results from accidentally using the program the "wrong" (but possible) way. This usage occurred on Windows 11.

Open WinSCP, no need to connect to remote site.
Open Options -> Preferences -> "Transfer" list item-> [select a preset; I selected Default] -> Edit.
Check "Set permissions:" so the octal settings becomes enabled
Click the "..." button on the octal settings group to open the visual checkbox editor.
Make any change in the popup*, but don't click "Close", just go around and click the "X" on the "Transfer Settings" window.
"Error Invalid access to memory"

* It appears not to cause error if you just open the permissions editor and then click the parent window's X without changing any settings, but it also did error when I simply clicked one permission checkbox, and then set it back the way it was, and then clicked the parent window's X.

<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 6.5.5

Error message:
Invalid access to memory.

Stack trace:
(00E0B25B) DefaultResult
(000B332F) ntdll.dll
(0007A56A) ntdll.dll.KiUserExceptionDispatcher
(004ACD27) Vcl::Forms::TCustomForm::ShowModal
(00D752AB) TCopyParamCustomDialog::Execute
(00D75127) DoCopyParamCustomDialog
(00DCEE54) TPreferencesDialog::AddEditCopyParam
(00DCEF5D) TPreferencesDialog::EditCopyParamButtonClick
(003A356D) Vcl::Controls::TWinControl::WndProc
(003C7B74) Vcl::Stdctrls::TButtonControl::WndProc
(003A36C7) Vcl::Controls::_17122
(003A356D) Vcl::Controls::TWinControl::WndProc
(003A2A78) Vcl::Controls::TWinControl::MainWndProc
(00204C90) System::Classes::_18364
(00038991) USER32.dll
(00026AE8) USER32.dll
(0002658B) USER32.dll
(00032DF7) USER32.dll
(0007A544) ntdll.dll.KiUserCallbackDispatcher
(0003FFC3) USER32.dll
(000262B1) USER32.dll.SendMessageW
(00073DE1) COMCTL32.DLL
(000893F7) COMCTL32.DLL
(00038991) USER32.dll
(00026AE8) USER32.dll
(00026255) USER32.dll.CallWindowProcW
(003A3675) Vcl::Controls::TWinControl::DefaultHandler
(003A356D) Vcl::Controls::TWinControl::WndProc
(003C7B74) Vcl::Stdctrls::TButtonControl::WndProc
(00204C90) System::Classes::_18364
(00038991) USER32.dll
(00026AE8) USER32.dll
(00025F75) USER32.dll
(00025ADB) USER32.dll.DispatchMessageW

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.

<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 5.17.8

Error message:
Invalid access to memory.

Stack trace:
(00E4803F) DefaultResult
(00087E3F) ntdll.dll
(000732D1) ntdll.dll.KiUserExceptionDispatcher
(00DF53AC) LocationProfilesDialog
(000522EB) TScpCommanderForm::DoOpenDirectoryDialog
(0001704F) TCustomScpExplorerForm::OpenDirectory
(00275D58) Vcl::Controls::TControl::Perform
(0027A52F) Vcl::Controls::TWinControl::IsControlMouseMsg
(0027A2A8) Vcl::Controls::TWinControl::MainWndProc
(003A58C4) System::Classes::_18201
(000435C9) USER32.dll
(000240D7) USER32.dll
(00023229) USER32.dll
(0002300B) USER32.dll.DispatchMessageW

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 5.9.5

Error message:
Zugriffsverletzung - ungültiger Zugriff auf den Speicher.

Stack trace:
(0080FB55) DefaultResult
(00081D3F) ntdll.dll
(0006F8EA) ntdll.dll.KiUserExceptionDispatcher
(00017A21) TCustomScpExplorerForm::FormCloseQuery
(0020DB2D) Vcl::Forms::TCustomForm::CloseQuery
(0024F2A9) Vcl::Controls::TWinControl::WndProc
(00209758) Vcl::Forms::TCustomForm::WndProc
(0080C7F8) Vclcommon::C2754_0
(0024E8F0) Vcl::Controls::TWinControl::MainWndProc
(0037326C) System::Classes::_18201
(0002C2B1) USER32.dll
(0000D885) USER32.dll
(0000D4BB) USER32.dll
(00017B07) USER32.dll
(0006F8C4) ntdll.dll.KiUserCallbackDispatcher
(0000E906) USER32.dll
(0003242C) UXTHEME.DLL
(000321B0) UXTHEME.DLL
(00025BB5) UXTHEME.DLL
(000255E3) UXTHEME.DLL
(0000EB91) USER32.dll
(0002C2B1) USER32.dll
(0000D885) USER32.dll
(0000CF12) USER32.dll.CallWindowProcW
(0024F3BA) Vcl::Controls::TWinControl::DefaultHandler
(0020CB3D) Vcl::Forms::TCustomForm::WMSysCommand
(0024F2A9) Vcl::Controls::TWinControl::WndProc
(00209758) Vcl::Forms::TCustomForm::WndProc
(0080C7F8) Vclcommon::C2754_0
(0024E8F0) Vcl::Controls::TWinControl::MainWndProc
(0037326C) System::Classes::_18201
(0002C2B1) USER32.dll
(0000D885) USER32.dll
(0000D4BB) USER32.dll
(00017B07) USER32.dll
(0006F8C4) ntdll.dll.KiUserCallbackDispatcher
(0000E906) USER32.dll
(0003242C) UXTHEME.DLL
(00032161) UXTHEME.DLL
(00025BB5) UXTHEME.DLL
(000255E3) UXTHEME.DLL
(

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 5.9.6

Error message:
Invalid access to memory.

Stack trace:
(00811209) DefaultResult
(000624F6) ntdll.dll
(0000F13E) ntdll.dll.KiUserExceptionDispatcher
(007CD71C) LocationProfilesDialog
(00044D67) TScpCommanderForm::DoOpenDirectoryDialog
(00014F4F) TCustomScpExplorerForm::OpenDirectory
(003B5680) System::Actions::TContainedActionList::ExecuteAction
(0019C7F9) Vcl::Actnlist::TCustomAction::Execute
(00373564) System::Classes::_18201
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167BF) USER32.dll
(00016885) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.

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 5.7.7

Error message:
Invalid access to memory.

Stack trace:
(00791401) DefaultResult
(0005A426) ntdll.dll
(0000F12E) ntdll.dll.KiUserExceptionDispatcher
(00015A18) TCustomScpExplorerForm::FormCloseQuery
(001DB781) Vcl::Forms::TCustomForm::CloseQuery
(0021C609) Vcl::Controls::TWinControl::WndProc
(001D73AC) Vcl::Forms::TCustomForm::WndProc
(0078E0D1) Vclcommon::C2516_0
(0021BC50) Vcl::Controls::TWinControl::MainWndProc
(0034059C) System::Classes::_18201
(000152F7) USER32.dll
(00015D35) USER32.dll
(00015DE3) USER32.dll
(00015E41) USER32.dll
(0000F107) 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
(0001FD22) USER32.dll
(0001FD48) USER32.dll.CallWindowProcW
(0021C71A) Vcl::Controls::TWinControl::DefaultHandler
(001DA791) Vcl::Forms::TCustomForm::WMSysCommand
(0021C609) Vcl::Controls::TWinControl::WndProc
(001D73AC) Vcl::Forms::TCustomForm::WndProc
(0078E0D1) Vclcommon::C2516_0
(0021BC50) Vcl::Controls::TWinControl::MainWndProc
(0034059C) System::Classes::_18201
(000152F7) USER32.dll
(00016311) USER32.dll.GetDC
(00015DE3) USER32.dll
(00015E41) USER32.dll
(0000F107) ntdll.dll.KiUserCallbackDispatcher
(00015A87) USER32.dll
(00016742) UXTHEME.DLL
(00025E80) UXTHEME.DLL
(0000FB0A)UXTHEME.DLL
(0000FB91)UXTHEME.DLL
(00016294) USE

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.