Custom Component OnMouseDown not working; - delphi

Question

I am trying to create a button based on TImage with 2 images governed by OnMouseDown.
The component shows the first image when running but I cannot get the OnMouseDown event to fire. I have looked through Stack Overflow related questions but cannot find an answer (Maybe I am asking the wrong question).
unit ImageBtn;
{$R resources.res resources.rc}
interface
uses WinTypes, WinProcs, Messages, SysUtils, Classes, Controls,
Forms, Graphics, Extctrls, AppEvnts, Buttons;
type
TImageBtn = class(TImage)
private
FCenter : Boolean;
FDoubleBuffered : Boolean;
procedure AutoInitialize;
procedure AutoDestroy;
procedure SetDoubleBuffered(Value : Boolean);
procedure WMSize(var Message: TWMSize); message WM_SIZE;
protected
procedure Click; override;
procedure Loaded; override;
procedure Paint; override;
procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Integer); override;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
published
property OnClick;
property OnDblClick;
property OnDragDrop;
property OnMouseDown;
property OnMouseMove;
property OnMouseUp;
property Center : Boolean read FCenter write FCenter default True;
property DoubleBuffered : Boolean read FDoubleBuffered write SetDoubleBuffered default True;
property Height;
property Proportional default True;
property Stretch default True;
property Width;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('dcs', [TImageBtn]);
end;
procedure TImageBtn.AutoInitialize;
begin
FCenter := True;
FDoubleBuffered := True;
Height := 29;
Proportional := True;
Stretch := True;
Width := 82;
Picture.Bitmap.LoadFromResourceName(HInstance,'BITMAP1');
end;
procedure TImageBtn.AutoDestroy;
begin
end;
procedure TImageBtn.MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
inherited;
MouseDown(Button, Shift, X, Y);
Picture.CleanupInstance;
Picture.Bitmap.LoadFromResourceName(HInstance,'BITMAP2');
end;
procedure TImageBtn.SetDoubleBuffered(Value : Boolean);
begin
FDoubleBuffered := Value;
end;
procedure TImageBtn.Click;
begin
inherited Click;
end;
constructor TImageBtn.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
AutoInitialize;
end;
destructor TImageBtn.Destroy;
begin
AutoDestroy;
inherited Destroy;
end;
procedure TImageBtn.Loaded;
begin
inherited Loaded;
end;
procedure TImageBtn.Paint;
begin
inherited Paint;
end;
procedure TImageBtn.WMSize(var Message: TWMSize);
var
W, H: Integer;
begin
inherited;
W := Width;
H := Height;
if (W <> Width) or (H <> Height) then
inherited SetBounds(Left, Top, W, H);
Message.Result := 0;
end;
end.
I have probably made a stupid mistake but I cannot find it. Can anyone help please? Delphi 7 and Windows 11.
Edit
Having read Blurry Sterk's comments, maybe I did not make the problem clear. The OnMouseDown event does not seem to fire but I cannot add a breakpoint as there are no blue points.
Edit2
Please find screenshot of the only lines that have a blue dot against them.
This is obviously related to why my code is not working.
Edit3
Thank you to everyone who replied. I followed the advice by removing the line MouseDown(Button, Shift, X, Y); and it worked. BTW I didn't want to use a TBitBtn because of the frame and alignment. The button needs a shadow. Thank you once again Tom Brunberg and Eirik A.