Images and Buttons not filling grid cells WPF XAML

Question

So I have 2 similar problems with the below image. The image is of a UserControl that has been added to a viewbox inside another UserControl:

Image

1. The button in the top-left does not fill the whole of the grid cell, but the image within it fills the whole button .I have been trying out different methods of binding button images. This is why this is not the same for the other buttons in the grid. However I can't see how they should differ

2. The black images on the centre top, left, right, and bottom buttons don't fill their buttons. However, when editing the code, the designer shows them filling those buttons. The code for these is identical to the ContentControl above, but has an image path linking to a completely black image instead.

Was wondering if these problems might be related or have a similar fix? I've tried using extra viewboxes and stretch to fill/ alignment parameters but they seem to make no difference.

EDIT:

Implementing Location.xaml in parent UserControl:

<Viewbox Grid.Row="1" Grid.Column="1" Grid.RowSpan="2" Margin="10 10 10 10">
            <ContentControl Content="{Binding CurrentLocationViewModel}">
                <ContentControl.Resources>
                    <DataTemplate DataType="{x:Type locationViewModel:SmallRoomViewModel}">
                        <locationView:SmallRoomView/>
                    </DataTemplate>

                    <DataTemplate DataType="{x:Type locationViewModel:LargeRoomViewModel}">
                        <locationView:LargeRoomView/>
                    </DataTemplate>
                </ContentControl.Resources>
            </ContentControl>
        </Viewbox>

SmallRoomView.xaml (the UserControl in the image):

 <Grid>
        <Grid.Resources>
            <Button x:Key="wallTile" x:Shared="false" PreviewMouseDown="OnMouseDown" Style="{StaticResource appWallTile}"/>
            <Button x:Key="floorTile" x:Shared="false" PreviewMouseDown="OnMouseDown" Style="{StaticResource appFloorTile}"/>
            <Button x:Key="doorTile" x:Shared="false"  PreviewMouseDown="OnMouseDown" Style="{StaticResource appDoorTile}"/>
        </Grid.Resources>
        
    <Button Grid.Row="0" Grid.Column="0" PreviewMouseDown="OnMouseDown">
        <Image Stretch="Fill" Source="{Binding tile0_0}"/>
    </Button>

    <ContentControl Grid.Row="0" Grid.Column="2" Content="{StaticResource doorTile}"/>
    <ContentControl Grid.Row="0" Grid.Column="3" Content="{StaticResource wallTile}"/>
    ...
</Grid>
        

App.xaml:

<Style x:Key="appDoorTile" TargetType="Button" x:Shared="false">
            <Setter Property="Content">
                <Setter.Value>
                    <Image Stretch="Fill" Source="./AllResources/images/tiles/doorTile.png"/>
                </Setter.Value>
            </Setter>
        </Style>
        <Style x:Key="appFloorTile" TargetType="Button" x:Shared="false">
            <Setter Property="Content">
                <Setter.Value>
                    <Image Stretch="Fill" Source="./AllResources/images/tiles/floors/floorTile.png"/>
                </Setter.Value>
            </Setter>
        </Style>

        <Style x:Key="appWallTile" TargetType="Button" x:Shared="false">
            <Setter Property="Content">
                <Setter.Value>
                    <Image Stretch="Fill" Source="./AllResources/images/tiles/walls/wallTile.png"/>
                </Setter.Value>
            </Setter>
        </Style>