Thank you for the details, i really appreciate it, still one thing you did not confirm yet, and will be really insightful.
On you Delphi is the stack cut at TApllicatiom.ProcessMessage too ? like WiWo screenshot, that is a problem not smaller the broken design !
If I run to a breakpoint in the OnClose handler the full call stack looks like this
Unit2.TForm2.FormClose($7F650010,caHide)
Vcl.Forms.TCustomForm.DoClose(???)
Vcl.Forms.TCustomForm.Close
Unit2.TForm2.Button1Click($3157C10)
Vcl.Controls.TControl.Click
Vcl.StdCtrls.TCustomButton.Click
Vcl.StdCtrls.TCustomButton.CNCommand(???)
Vcl.Controls.TControl.WndProc((48401, 1634, 591458, 0, 1634, 0, (), 1634, 9, (), 0, 0, ()))
Vcl.Controls.TWinControl.WndProc((48401, 1634, 591458, 0, 1634, 0, (), 1634, 9, (), 0, 0, ()))
Vcl.StdCtrls.TButtonControl.WndProc((48401, 1634, 591458, 0, 1634, 0, (), 1634, 9, (), 0, 0, ()))
Vcl.Controls.TControl.Perform(???,???,591458)
Vcl.Controls.DoControlMsg(???,(no value))
Vcl.Controls.TWinControl.WMCommand((273, (), 1634, 0, (), 591458, 0))
Vcl.Forms.TCustomForm.WMCommand((273, (), 1634, 0, (), 591458, 0))
Vcl.Controls.TControl.WndProc((273, 1634, 591458, 0, 1634, 0, (), 1634, 9, (), 0, 0, ()))
Vcl.Controls.TWinControl.WndProc((273, 1634, 591458, 0, 1634, 0, (), 1634, 9, (), 0, 0, ()))
Vcl.Forms.TCustomForm.WndProc((273, 1634, 591458, 0, 1634, 0, (), 1634, 9, (), 0, 0, ()))
Vcl.Controls.TWinControl.MainWndProc(???)
System.Classes.StdWndProc(657428,273,1634,591458)
:75d40eab USER32.AddClipboardFormatListener + 0x4b
:75d37e5a ; C:\WINDOWS\SysWOW64\USER32.dll
:75d37239 ; C:\WINDOWS\SysWOW64\USER32.dll
:75d3587f USER32.SendMessageW + 0x6f
:6e0c6618 ; C:\WINDOWS\WinSxS\x86_microsoft.windows.common-controls_6595b64144ccf1df_6.0.19041.3636_none_a863 d714867441db\comctl32.dll
:6e105f33 ; C:\WINDOWS\WinSxS\x86_microsoft.windows.common-controls_6595b64144ccf1df_6.0.19041.3636_none_a863 d714867441db\comctl32.dll
:75d40eab USER32.AddClipboardFormatListener + 0x4b
:75d37e5a ; C:\WINDOWS\SysWOW64\USER32.dll
:75d37537 ; C:\WINDOWS\SysWOW64\USER32.dll
:75d356db USER32.CallWindowProcW + 0x1b
Vcl.Controls.TWinControl.DefaultHandler(???)
:005ff9e2 TWinControl.DefaultHandler + $136
:005ff88c TWinControl.WndProc + $6AC
:00614f89 TButtonControl.WndProc + $71
:00588db2 StdWndProc + $16
:75d40eab USER32.AddClipboardFormatListener + 0x4b
:75d37e5a ; C:\WINDOWS\SysWOW64\USER32.dll
:75d35bca ; C:\WINDOWS\SysWOW64\USER32.dll
:75d35990 USER32.DispatchMessageW + 0x10