Or did you maybe try to do the export before actually finishing the chamfers? Some commands like Chamfer or Fillet have a final stage in the command where you need to push "Done" or right-click in a viewport to finalize the command.

If you tried to export before actually finishing the command the chamfer will get canceled.

When I load your IGES file here I only see the chamfers on one side of the object as I showed highlighted in that previous screenshot, the opposite side of your IGES file looks exactly like your render screenshot, like this - no chamfers present on that other side:



So as far as I can tell the render that you showed looks the same as this, sorry if I am not understanding what you are getting at...

Maybe you thought you did a chamfer but did not finish the command ?

- Michael