<p>Thanks for sharing your experience. I've now fixed mine. Not a loose screw, though.</p>
<p>I first removed ten screws on the bottom and eight on the back, after which the housing easily slid off. I could then see lots of interesting mechanisms. I manually rotated the stepping motor by gripping a bit of black plastic in order to see more. (What you can see without this depends on where it was when you shut down the machine.)</p>
<p>I didn't see anything loose, however. (There were several screws that I can imagine could get loose, though.)</p>
<p>Looking for what might cause the film holder to stall, I did see what looked like they could be sensors on the left side of the machine (when facing its front). These consist of three pairs of knobs, though which a ridge on the left side of the film holder passes. (You can see this ridge on all the film holders, on the left side as you insert the film holder, with the right side instead having places for the gears that move it to grip.) I speculate that these are either optical sensors, or perhaps sensors that look at the change in capacitance when the plastic ridge is betwen the two knobs. I cleaned them all (especially between the two knobs) with a Q-tip cotton swab.</p>
<p>The scanner now works fine. Presumably there was dust or some such on these sensors that caused them to think the film holder was positioned someplace it wasn't, with the bad results I observed.</p>
<p>For future reference, I note that one should actually be able to reach in and clean between these knobs by just opening the front door where the film holder is inserted (they're on the left), without having to take the scanner apart. You would need something longer than a Q-tip, however.</p>