RTAB-map with robot_localization

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I'm building a simple differential drive robot with the kinect+fake laser setup from the tutorials, and now I'm trying to do some navigation with move_base.

my transforms look like this, except instead of IMU I'm combining wheel encoder odometry and visual odometry from RTAB-map.

when visual odometry is used alone, it's mostly fine until the robot gets close to a wall or something. I'm trying to use robot_localization to combine the two odometries and feed it into RTAB-map as /odom_filtered.

en<node pkg="robot_localization" type="ekf_localization_node" name="ekf_localization" clear_params="true">
 <param name="frequency" value="20"/>
 <param name="sensor_timeout" value="1.5"/>
 <param name="two_d_mode" value="true"/>
 <param name="map_frame" value="map"/>
 <param name="odom_frame" value="odom"/>
 <param name="base_link_frame" value="base_link"/>
 <param name="world_frame" value="odom"/>
 <param name="transform_time_offset" value="0.0"/>

 <param name="odom0" value="/fake_odom"/>

 <rosparam param="odom0_config">[false, false, false,
                              false, false, false,
                              true, true, false,
                              false, false, true,
                              false, false, false]</rosparam>
 <param name="odom0_differential" value="true"/>

 <param name="odom1" value="/rtabmap/visual_odom"/>

 <rosparam param="odom1_config">[true, true, false,
                              false, false, true,
                              false, false, false,
                              false, false, false,
                              false, false, false]</rosparam>
 <param name="odom1_differential" value="false"/>

</node>

With robot_localization, after a while the map looks like this:

the 3d and 2d map becomes chaotic and shifts around each frame.

my view_frames looks like this:

any idea what I'm doing wrong? The visual odometry is only published at around 1hz, could that be a problem?