URDF broken rendering in RVIZ

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I need help understanding why my urdf keeps breaking in Rviz. (I apologise for the length of this question).

The problem I am experiencing is my robot only part renders in Rviz. To make matters worse, I am loading the same urdf from two seperate packages and both result in widely difference output in Rviz.

I've followed and almost finished the ROS URDF tutorial. From that tutorial I have the following xacro:

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="R2D2">

    <xacro:property name="bot" value="R2D2"/>

    <material name="blue">
        <color rgba="0.0 0.0 1.0 1.0"/>
    </material>
    <material name="white">
        <color rgba="1.0 1.0 1.0 1.0"/>
    </material>
    <material name="green">
        <color rgba="0.0 1.0 0.0 1.0"/>
    </material>
    <material name="red">
        <color rgba="1.0 0.0 0.0 1.0"/>
    </material>
    <material name="black">
        <color rgba="0.0 0.0 0.0 1.0"/>
    </material>

    <!-- Base Link -->

    <xacro:property name="base_link_radius" value="0.2"/>
    <xacro:property name="base_link_length" value="0.6"/>

    <link name="base_link">
        <visual name="">
            <geometry>
                <cylinder radius="${base_link_radius}" length="${base_link_length}"/>
            </geometry>
            <material name="blue"/>
        </visual>
        <collision>
            <geometry>
                <cylinder radius="${base_link_radius}" length="${base_link_length}"/>
            </geometry>
        </collision>
        <inertial>
            <mass value="10"/>
            <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
        </inertial>
    </link>

    <!-- LEGS -->
    <xacro:macro name="leg" params="prefix flip">

        <xacro:property name="leg_dimensions" value="0.6 0.1 0.2"/>

        <link name="${prefix}_leg_link">
            <visual>
                <geometry>
                    <box size="${leg_dimensions}"/>
                </geometry>
                <origin xyz="0.0 0.0 -0.3" rpy="0.0 1.57075 0.0"/>
                <material name="white"/>
            </visual>
            <collision>
                <geometry>
                    <box size="${leg_dimensions}"/>
                </geometry>
                <origin xyz="0.0 0.0 -0.3" rpy="0.0 1.57075 0.0"/>
            </collision>
            <inertial>
                <mass value="10"/>
                <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
            </inertial>
        </link>

        <joint name="base_to_${prefix}_leg" type="fixed">
            <parent link="base_link"/>
            <child link="${prefix}_leg_link"/>
            <origin xyz="0.0 ${flip * -0.22} 0.25" rpy="0.0 0.0 0.0"/>
        </joint>
    </xacro:macro>

    <xacro:leg prefix="right" flip="1" />
    <xacro:leg prefix="left" flip="-1"/>

    <!-- Leg bases -->
    <xacro:macro name="legbase" params="prefix switch">
        <xacro:property name="legbase_dimensions" value="0.4 0.1 0.1"/>
        <link name="${prefix}_leg_base_link">
            <visual name="">
                <geometry>
                    <box size="${legbase_dimensions}"/>
                </geometry>
                <material name="white"/>
            </visual>
            <collision>
                <geometry>
                    <box size="${legbase_dimensions}"/>
                </geometry>
            </collision>
            <inertial>
                <mass value="10.0"/>
                <inertia ixx="0.4" ixy="0.0 ...