Few years ago friend gave me a broken scanner. In Windows it always said "Paper jammed". I opened it and just wanted to short paper sensor, but this scanner was

Few years ago friend gave me a broken scanner. In Windows it always said "Paper jammed". I opened it and just wanted to short paper sensor, but this scanner was too "smart". Instead of single sensor there were two sensors next to each other and the scanner was using them to calculate speed of paper and if it was outside of some range it called an error. I tried sane on Linux and got similar error. But on Linux I had source code so I found exact error message, commented that single line out, recompiled and it worked like a charm.