Hi Franck,
Here are some other suggestions to reduce flicker and popping.
Popping can occur when gaps appear in geometry in between frames.
To get gap free geometry you need to disable both microvertex jittering and detail jittering and paste the following into the internal network of the render node:
<terragen_clip>
<render_subdiv_settings
fully_adaptive = "0"
force_all_edges = "1"
>
</render_subdiv_settings>
</terragen_clip>
Also, to reduce flicker you can disable "jitter shading points" in this render subdiv settings node.
Along with some ray detail region padding and high GI sampling you shouldn't get much flicker and popping anymore.
Flickering wasn't a real issue anyway

We should render out an animation together sometime, would that be an idea?

Cheers,
Martin