I managed to recreate the problem, as you say it was not the .mtl file, it was caused by a parameter in the .properties file. The furniture could be used in the plan, but an error occurred when selecting "save". To solve the problem I deleted all instances of the imported furniture, corrected the ...

Hi,

I have been using Sweet Home 3D successfully for a while without any errors when it failed to save the model. The automatic saves every 10 minutes had failed as well, so I know roughly when the problem started.

The error I got was

Can't save home in:
/home/..etc
java.lang ...