I have seen a post similar to this before but about pipework but can't for the life of me find the original post...
When using the design to fabrication tools, SOMETIMES the shoes convert and other times it just cuts straight through and messes up (see attached). I have not found any trends of when it does it or when not its both spiral and rectangular that it will sometimes work on. The image attached is the same size duct in areas where it has worked and not worked.
Can anyone shed any light on this please?