Vector pictures and scruffy line ends

Hi everybody,

this is my first post to this forum so condolences for all for possible etiquette mistakes.

I'm using CorelDraw Technical Suite X6 to handle technical drawings, which are been printed from the Autodesk Inventor Publisher (vector pictures). When I bring them in Corel and re-open the saved file, pictures look like in the sample below. It looks like the program is drying to combine lines open ends.

How to solve this? I have no idea. 

I tried to re-install the program but no effect. Autodesk spokesman says that the problem is in CorelDraw.

 

Thanks!

Tom