Emmanuel, I did not made any update on my computer. In fact the 2D object rendering and also the 3D rendering where very slow since a while.
I discovered then the plugins so I wanted to test them (not to resolve the issue but just to test the plugin), so without any other change but after installing ...

Hello,

The issue has been fixed on my side by installing the plugins "AdvancedSettings_PhotoRendering-1.3.1.sh3p" and "PhotoVideoRendering-1.8.zip". You can find them here: "http://www.sweethome3d.com/plugins.jsp".

Good luck