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### Complex model sometimes (1:4x) opens gazebo with black screen

Hi,

I'm running a (seemingly) reasonably complex model where a population grid is created of very simple rectangular wall parts. Like so:

<population name="dirty_grid">
<model name="dirty_element">
<include>
<uri>model://dirty_element2</uri>
</include>
</model>
<pose>0.3 0 1.225 1.5707 0 1.5707</pose>
<distribution>
<type>grid</type>
<rows>5</rows>
<cols>5</cols>
<step>0.0125 0.0125 0</step>
</distribution>
</population>


The problem is that Gazebo sometimes doesn't open correctly (about 1:4 times). It starts at 0.1x realtime and slowly moves up (in about 3 seconds) but when it is at 0.9x realtime the screen is still black. I can imagine this is the time that Gazebo takes to create the population of models but don't understand why it sometimes works fine and other times does not.

Have tried debugging but I can't see anything different from when it works fine and when a black screen appears. Any tips?