I don’t have a good explanation as to why you would have such a large gap to the outside of the cabinet off the top of my head. We do usually recommend using the story stick to lay out multiple cabinets when possible, which does fix the issue, but when drawing a single, frameless cabinet, it is possible to have the doors and drawers go all the way from side to side. Is it possible for you to send us a copy of your settings file?
Go to File->CabWriter->Save CabWriter Defaults and choose a name for the file. Then, go to your plugins folder then into the cabwriter/cabwriter_defaults folder and grab that file and email it to us or attach it to this post. We can take a look at your settings and see if we can spot what is wrong.