Thomasa88, the bug #943 / #864 isn't the same as the original post. The crash you encountered happens when Sweet Home 3D tries to create a small screenshot of the imported 3D model at the last step of the wizard.
But thanks for reporting a solution [:)]

I have exactly this problem with MacOS on 6.5.2.

100% reproducible with my MacPro running MacOS Catalina and my old MacBook Pro running MacOS HighSierra.

Is there a downgrade version ?

I totally understand that i have no right to complain about free SW, but please fix it [:x]