TAdvStringGrid Button Drawing

I've added some buttons to the fixed column of a TAdvStringGrid and noticed an inconsistency.

The button in the top/left (fixed row 0, column 0) doesn't react visually to the mouse click.  The OnButtonClick event fires, but it just doesn't look like it's working to the user.

The buttons added to the fixed column (0) for the non-fixed rows do show the button press correctly.

Confusingly, when I try this on a new project none of the buttons visually press in.  Is it linked to the appearance of the cells ?

No solution for this ?