I have upgraded to 0.9.19 and having issues with Optimization Settings in 0.9.17 Group Optimization was working but I just loaded an old file and it is not.
You can see in the following pic that I have parts grouped.
And here I have Optimization Settings set to Order By Group only.
Here is my preview
It is not doing the group as it looks like it is doing Order by Layer???
This is causing a shift on my laser that i have not resolved yet. But i know when I group them the shift in my cuts does not happen.