[Pandysloo]

Take off the lens and fire the shutter, look at the mirror's action. Is it rising all the way to the top? Before the shutter travels? Open the back and, with the lens removed fire the shutter observing the action at various speeds. Point the camera at a well lit blank white wall for these tests. This should tell you if it is the mirror not getting out of the way soon enough or, if it is the first shutter segment dragging, allowing the second segment to catch up and end the exposure.

I tried that but there's no noticeable lag or discrepancy. I figure that at 1/500 and 1/1000 it is too fast to really see anyway...

My two cents (sense?): I have a feeling that there is a tiny bit of oil in the shutter blades, preventing clean, quick movement.

You mean like this?Photo Feb 15, 9 25 23 AM.jpg

I should note that when I bought it the ebay store claimed all cameras sold were CLA'd, tested, and verified fully functional. I'm hoping he's willing to exchange it for a working one, even though the 90-day money back guarantee expired 2 days ago...