I would need to know which file(s) to have a look - if there is an error I can fix it -
I have no clue if you are talking about new files, old files, or where to look because there are lots of files, in lots of locations, and lots of possible causes of lots and lots of potential errors - and errors are so rare I can't imagine what it might be
and it might not matter but I would think there must be additional more specific error information -
I've never known autocad to be ambiguous about DXF errors - it typically displays a specific error message and the line number where the error occurred - then it says press enter - when you press enter it aborts the open operation - it does not close the drawing per se because it never opened it
I'm pretty sure it would not simply say that and then close the drawing