simon, all your jobs of comment #94 and comment #95 have "usb-unidir" arttributes. So the forced uni-directional mode was not stopped for you.
Sorry, I did not give the correct command to remove the forced uni-directional mode. Run the command
lpadmin -p Lexmark_S300S400_Series -R usb-unidir-default
Note the "-default" at the end. Look into your error_log and check whether you get a line containing "Deleting usb-unidir-default". After that, repeat your tests.
simon, all your jobs of comment #94 and comment #95 have "usb-unidir" arttributes. So the forced uni-directional mode was not stopped for you.
Sorry, I did not give the correct command to remove the forced uni-directional mode. Run the command
lpadmin -p Lexmark_ S300S400_ Series -R usb-unidir-default
Note the "-default" at the end. Look into your error_log and check whether you get a line containing "Deleting usb-unidir- default" . After that, repeat your tests.