Quote Originally Posted by polyglot View Post
Maybe you accidentally put one of the negs in the scanner upside down. The first one's pretty symmetric...

I also note the notch in the film-gate on the top-right of the first one is not present on the second though it could be present/invisible at left. I reckon one of them is scanned backwards and it's a winding-on issue as described above.
There were just quickly scanned to show the problem so they could have been in any direction. Also didn't blow off any dust :-)