I noticed this issue last year while teaching from the 2015 book. When you get to Lesson 4, Page 160, Step 10 - sometimes flattening the part results in an error: "The part contains features that cannot be unbent." The "completed" part also has this same issue but if you follow this workflow you can "fix" the problem: suppress the cut extrude, un-suppress the cut, un-suppress the pattern, roll to end.

This issue is still not resolved in the 2016 Training Files (for the "completed" part or the case study part). One way to get around this when delivering the case study is to:

1. Flatten the part

2. While still in the flat, roll back between Flatten-Bends1 and Process-Bens1

3. Create the sketches, cut and pattern

4. Roll to end

Now you should be able to un-flatten and flatten without getting the error. Has anyone else had issues with this?