Custom EKF with lockstep SITL enabled

I’m implementing a custom EKF to be used with the Gazebo SITL. I want it to be able to work with lockstep enabled. In my code, I used the same function calls to the lockstep scheduler as in ekf2_main.cpp, in particular lockstep_register_component and lockstep_progress. I verified via Mavlink console that my EKF estimator is correctly loaded and that EKF2 is disabled. Yet when I run the simulation with lockstep enabled, it gets stuck with Gazebo becoming unresponsive. I think that I am missing some message that prevents PX4 from sending the actuator command that Gazebo is waiting for but cannot figure out what it is. Any help or more detailed info on the flow of the lockstep relevant routines and messages especially during initialization of the SITL would be greatly appreciated.