We were testing one of our Kodak i4200's. It would scan the first page but immediately jam with that 1st page stuck in the scanner throat. The scanner displayed a U8 error on its front panel.
We tried the usual steps to clear this problem:
Made sure the paper throat path in the scanner was completely clear of any debris (e.g... paper, torn paper, staples).
Inspected the main paper feed drive rollers for damage or being worn down.
Checked that all paper exit rollers spin freely.
Tried a different piece of paper to test with.
Looked in the scanner user guide, said it was a multi-feed error. But since we were only scanning 1 page we thought how could this be a multi-feed error?
Everything looked okay, but we kept getting the U8 error. The first scanned page would feed through the feed rollers but come to a stop just after passing through the main feed drive roller.
We noticed that when we pressed in the paper thickness lever on the lower left-hand front corner of the scanner, the scanner would scan okay. So we spent ages looking at the lower grey brake roller and how it was sitting. Concluded that even though it was tight and hardly rolled that was pretty much how it feels on other i4200's that don't exhibit the same problem.
During our tests we luckily switched over to another scanning profile and then the i4200 scanner then worked perfectly. This was fortunate because we now knew it had to be a software configuration issue, not a scanner hardware fault causing the U8 error. We were able to compare the scanner profile that worked to the scanner profile that didn't.
We noticed that the bad scanner profile was set to use multi-feed detection with the parameter value set to = Both. Both mean that the scanner uses both the ultrasonic detector and paper length detection methods.
When we set the bad profile to use multi-feed detection using just the ultrasonic detection only, the scanner worked perfectly. with no U8 error. When we set the bad profile to multi-feed detection using just paper length detection only, the scanner gave us the U8 error. A closer inspection of the paper length setting revealed that the length was set to exactly 11.69 inches (i.e. the exact physical length of A4 paper).
In a scanner that has scanned 1000's of pages the motor and rollers may cause a slight delay in scan time, which may easily result in the scanned image being between 3 to 30 pixels longer than the physical paper length. This causes the scanned image to exceed the physical paper length (A4 11.69 inches) and hence triggered the multi-feed paper length detection logic to stop the scanner with a U8 error on its display.
To fix this issue you just need to allow a bit of 'wiggle' room in the paper length detection setting. Increase the value by no more than 5% of the physical paper length. We set our paper length detection figure at 12.00 inches (approximately 3% wiggle room) , retested and the scanner no longer stops with a U8 error.
Whether you have a Kodak, Fujitsu, Canon or another brand of scanner it would good advice to remember to always set multi-feed detection paper length detection to 3%-5% longer than the physical paper length. We spoke to Kodak and they told us they prefer to use an +5% added to physical page paper length.
For example when scanning A4 pages in portrait setting the paper page length detection figure to 12.27 inches (i.e. A4 paper length of 11.69 inches + 5% extra being 0.58 inches) will help stop the scanner giving excessive multi-feed detection errors just because of slight variations in scanned image page length due to any delays in feeding paper throw the scanner (due to scanner age or usage).
This should save you putting in a service call for paper jam errors when the real issue is just the scanner configuration settings.