The Asprise TWAIN library has the following problem:
For black&white and grey scans (i.e. all but color), each line is shifted the same amount against the last, resulting in images looking tilted, and sometimes even in a crash of the Java virtual machine. It happens not always, but apparently depending in the # of pixels per line.
The cause is probably that the # of bytes per line is not padded correctly to get a multiple of 4, which is required for Windows bitmaps.
RGB Color scans have 4 bytes/pixel, so there is no problem with these.
Workaround: Turn automatic border detection off and, for fixed paper size, try out slightly different resolutions until the image looks right. Then, with these parameters, it always does.
With Fujitsu scanners we never experienced the problem, they seem to always produce lines with a multiple of 4 bytes, even in black&white and grey.
I kept asking Asprise to fix this problem, with no avail.
We finally changed our TWAIN library to Gnome Morena.