TL;DR:

Because you checked the "Process" option in Database > Fittings > Pattern Switches > Developments > Folding Lines:

This even messed up Nest Prints:

If you checked "Check for Oversize before Nesting" in Database > Manufacturing > Oversize Options:

It would be even ask you to check Oversized Item again even if you have already checked when accepting item:

After that, the nested sheets went horrible:

And it caused a lot of waste:

It seems that CAMduct consider the "fold line" as part of this Part.

According to the doc:

Folding Lines: This option specifies how the folding lines will be treated.
Display: Displays the folding lines seen on folded or rolled fittings when developed.
Process: Processes folding lines using an available marking tool. If the Process switch is selected, and no marking tool is present, the marking line may be traced by the cutting head. This may lead to large, unnecessary moves across the table.

I guess, if your machine does not have "an available marking tool", then you should not check "Process" for Folding Lines.

In my mind, Folding Lines are very helpful, both on the cut out metal part and on printed worksheets. But it is so weird that only Radius Offset pattern could show Folding Lines.

If you check "Process" for Folding Lines, the lines will also show on Nest Labels and Work Sheet. If uncheck, they will not show on anywhere.