# Why does Blender crash when I append this group?

I have made a group composed of four mesh objects and a curve object. Two of the objects have array modifiers, one has a mirror modifier. I have tried several times to import it to another file, and Blender crashes every time.

This group was first built as part of a larger file, that I then decided to split up into a set of assets. The group was first created in that larger file. When I tried to append it in a new file, Blender crashed.

Lazily, I decided to simply delete everything in the larger file that wasn't in that group and save it as a separate file, but then when I decided to append the new asset file in something else, Blender crashed again.

I found that there was data for several other groups in the file, so I selected everything, pressed Shift-Ctrl-Alt-G, and deleted the objects from all groups. I saved the file, closed it and reopened it, and set up a new group. Then I tried to append the group again, and Blender crashed.

So I opened a new file, appended the objects for the group, and created a new group for them, and saved that. I tried to append that new file's group to another file, and Blender crashed.

Appending other objects works fine, including ones that also have mirror and array modifiers. I can't see anything wrong with this file. How do I solve this problem?

Blender 2.78c running on Ubuntu Budgie 16.10.

[I am working on Windows but it was also crashing here.] You have an object called MiddleMirrorPipeHolder that is a child of ParabolicMirrors - but - you also use MiddleMirrorPipeHolder as the mirror object for ParabolicMirrors. I believe that is confusing Blender. Removing the parenting will allow you to append your model. I suggest you use an empty as mirror object.

• Yep, that was it. Thank you very much. (I'm always especially impressed when i get answers in under an hour on the weekend.) – kim holder Jun 17 '17 at 23:13

I tried starting Blender 2.77 from the command line to see if it generated any warnings and got this message in the terminal when I tried to append the ParabolicMirrorThermalUnit group:

Dependency cycle detected:
MiddleMirrorPipeHolder depends on ParabolicMirrors through Parent.
ParabolicMirrors depends on MiddleMirrorPipeHolder through Mirror Modifier.


But Blender 2.77 didn't crash after appending to a default file. However 2.78b did crash so maybe there is some kind of bug in Blender 2.78 when dealing with cyclic dependencies. You should probably submit a bug report.

• Thanks. I will do so. And also, it never occurred to me to look at terminal messages - that is a valuable thing for the future. – kim holder Jun 18 '17 at 20:31