Unexpected results from robot_localization

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I'm playing with robot_localization trying to get position estimate in a very simple scenario. My emulated vehicle is starting from position x=0, y=0, orientation=0, and receives the following velocity command at /cmd_vel for 10 seconds: linear = (1,0,0), angular = (0,0,0). I expect my base_link to be at x=10, y=0 after 10 seconds. Instead it drifts off as shown on the screenshot attached:

Screenshot and bagfile on Google Drive

I've added my bagfile as well with /cmd_vel, /gps/fix, /imu/data, /odom/twist and this is my launch file:

<launch>
  <node name="ekf_loc_odom" pkg="robot_localization" type="ekf_localization_node">
    <param name="world_frame" value="odom"/>
    <param name="two_d_mode" value="true"/>
    <param name="frequency" value="10"/>
    <param name="twist0" value="/odom/twist"/>
    <rosparam param="twist0_config">[ false, false, false,
                                      false, false, false,
                                       true,  true, false,
                                      false, false,  true,
                                      false, false, false]</rosparam>
  </node>
  <node name="ekf_loc_map" pkg="robot_localization" type="ekf_localization_node">
    <param name="world_frame" value="map"/>
    <param name="two_d_mode" value="true"/>
    <param name="frequency" value="10"/>
    <param name="odom0" value="/odometry/gps"/>
    <rosparam param="odom0_config">[ true,  true, false,
                                    false, false, false,
                                    false, false, false,
                                    false, false, false,
                                    false, false, false]</rosparam>
    <param name="odom0_differential" value="false"/>
    <param name="imu0" value="/imu/data"/>
    <rosparam param="imu0_config">[false, false, false,
                                   false, false,  true,
                                   false, false, false,
                                   false, false, false,
                                   false, false, false]</rosparam>
    <param name="imu0_differential" value="false"/>
  </node>
  <node name="navsat_transform" pkg="robot_localization" type="navsat_transform_node">
    <param name="magnetic_declination_radians" value="0"/>
    <param name="zero_altitude" value="true"/>
  </node>
  <node name="vehicle_emu" pkg="mario_control" type="vehicle_emu.py">
    <remap from="twist" to="odom/twist"/>
    <remap from="fix" to="gps/fix"/>
    <remap from="imu" to="imu/data"/>
  </node>
</launch>

I'm not sure if it's related but robot_localization throws these warnings:

[ WARN] [1595237876.432141012]: Transform from base_link to odom was unavailable for the time requested. Using latest instead.
[ WARN] [1595237876.432755891]: Transform from odom to map was unavailable for the time requested. Using latest instead.
[ WARN] [1595237879.429787646]: Transform from base_link to odom was unavailable for the time requested. Using latest instead.
[ WARN] [1595237879.430319590]: Transform from odom to map was unavailable for the time requested. Using latest instead.

Could someone help me with pointing out what am I doing wrong? Thank you!

EDIT-1: Just in case it helps, here's an example of the sensor_msgs/Imu messages published on /imu/data:

header: 
  seq: 672
  stamp: 
    secs: 1595237860
    nsecs: 798180103
  frame_id: "base_link"
orientation: 
  x: 0.0
  y: 0.0
  z: 0.0
  w: 1.0
orientation_covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
angular_velocity: 
  x: 0.0
  y: 0.0
  z: 0.0
angular_velocity_covariance: [-1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
linear_acceleration: 
  x: 0.0
  y: 0.0
  z ...