Thanks for posting these videos. Really strange issue that I still can't reproduce under macOS 10.10 and 10.12
If needed, all installers are available here so maybe, you're not obliged to go back to such an old version.
Could you try to install Java 8 and run Sweet Home 3D 5.5 from its Jar Executable or Java Web Start versions?
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Emmanuel Puybaret, Sweet Home 3D creator
