Attempting to import .obj

I am trying to import .obj files for my 3d models and I’m running into a problem.

When importing the file and grouping to make a 3d model then selecting an operation such as outline the slicing I always get the warning as follows:

invalid bottom 10>=bounds z max 10. Z bottom cannot be above or equal to Z top.

Is this caused by a faulty file or have I set something wrong?

I haven’t seen this. Is your stock offset or absolute? Is the stock larger than the object? Can you send me the .obj file?