Question about the <max_step_size> in px4 SITL empty.world

hello everyone
I meet a question about the world files in SITL.
when I use UAV simulation in gazebo, the some parameters in world file are:

<max_step_size>0.004</max_step_size>
<real_time_factor>1</real_time_factor>
<real_time_update_rate>250</real_time_update_rate>

when I add other robot models such as manipulator in this world, the UAV works well, but other robots maybe work bad.
the main problem is:

<max_step_size> and <real_time_update_rate>

I konw px4 needs that:

<max_step_size>0.004</max_step_size>
<real_time_update_rate>250</real_time_update_rate>

but other robots or some plugins need:

<max_step_size>0.001</max_step_size>
<real_time_update_rate>1000</real_time_update_rate>

I have a plugin (vacuum) on manipulator , and when the max_steo_size is 0.004, vacuum can’t work well.
I use vacuum by libgazebo_ros_vacuum_gripper.so in xacro file, so I can not modify the parameters in .so file.

how can I fix this problem?