Custom control with Entry, ReturnCommand not working

Question

I built a simple adaptation of the Entry control as follows:

<?xml version="1.0" encoding="utf-8" ?>
<Grid xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
  xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
  xmlns:local="clr-namespace:B1WApp.CustomControls"
  x:Class="B1WApp.CustomControls.UI5Entry"
  x:DataType="local:UI5Entry">

<Border StrokeShape="RoundRectangle 5" 
        Stroke="{StaticResource SAPFieldBackground}"
        BackgroundColor="{StaticResource SAPFieldBorderColor}"
        Padding="1"
        x:Name="OuterBorder">
    <Border StrokeShape="RoundRectangle 4" 
            Stroke="{StaticResource SAPFieldBackground}"
            BackgroundColor="{StaticResource SAPFieldBackground}">
        <Entry Text="{Binding Path=Text}"
               Placeholder="{Binding Path=Placeholder}"
               PlaceholderColor="{StaticResource SAPFieldPlaceholderColor}"
               ReturnType="{Binding Path=ReturnType}"
               IsPassword="{Binding Path=IsPassword}"
               Margin="{OnPlatform Default='0', Android='0,-8,0,-8'}"
               Focused="Entry_Focused"
               Unfocused="Entry_Unfocused"
               Completed="Entry_Completed"
               ReturnCommand="{Binding Path=ReturnCommand}"/>
    </Border>
</Border>
</Grid>

In code-behind I have:

using System.Windows.Input;

public partial class UI5Entry : Grid
{
    public UI5Entry()
    {
        InitializeComponent();

        this.BindingContext = this;
    }

// additional code omitted for brevity

    public static readonly BindableProperty ReturnCommandProperty = BindableProperty.Create(
        propertyName: nameof(ReturnCommand),
        returnType: typeof(ICommand),
        declaringType: typeof(UI5Entry),
        defaultValue: null,
        defaultBindingMode: BindingMode.OneWay);

    public ICommand ReturnCommand
    {
        get => (ICommand)GetValue(ReturnCommandProperty);
        set => SetValue(ReturnCommandProperty, value);
    }
}

However, when I use the control, the ReturnCommand never fires. The other properties work fine, however. Am I missing something here?

<customControls:UI5Entry 
                ReturnType="Search"
                Placeholder="Digita/escanea # de doc."
                Text="{Binding SearchText, Mode=TwoWay}"
                ReturnCommand="{Binding SearchForBaseDocumentsCommand}"
                />

Thanks in advance for any hints on this issue.

Best regards,

Joerg.