Filter failed error for Kyocera printers in Linux is caused by a BUG in the device driver

I recently got a new Kyocera FS-1025MFP unit and the print jobs would stop if there are Chinese characters in the job title. The OS is Ubuntu 16.04. Specifically, the error message was either "filter failed" or "filter crashed". Upon checking the CUPS error messages, I discovered that this was due to an error signal 6 returned by the "rastertokpsl" program shipped with the Kyocera driver.

To correct this problem:

1. Download, and install the Kyocera driver by running install.sh as root. This will copy the printer's PPD file to /usr/share/cups/model/Kyocera/ and the rastertokpsl program to /usr/lib/cups/filter/.

2. Create a wrapper for rastertokpsl by:

sudo nano /usr/lib/cups/filter/rastertokpsl-fixed

and then insert the following text:

#!/bin/bash
jobname=$(echo $3 | egrep -o '[[:alnum:]]' | tr -d '\n' | tail -c 20)
path=/usr/lib/cups/filter
$path/rastertokpsl "$1" "$2" "$jobname" "$4" "$5"

3. Make sure that the wrapper has execution permission:

sudo chmod a+x /usr/lib/cups/filter/rastertokpsl-fixed

4. Edit the PPD file specific to your printer model as found in /usr/share/cups/model/Kyocera/. For instance, mine is an FS-1025MFP and the file name is Kyocera_FS-1025MFPGDI.ppd. The only modification that should be made is the cupsFilter line (line 55 in my case):
Find:

*cupsFilter: "application/vnd.cups-raster 0 /usr/lib/cups/filter/rastertokpsl"

and replace the line with:

*cupsFilter: "application/vnd.cups-raster 0 /usr/lib/cups/filter/rastertokpsl-fixed"

The above steps should fix the problem. Alternatively, you may edit the PPD file shipped with the installation package and create the rastertokpsl-fixed wrapper for the installation files, and add the wrapper into install.sh so that you can be able to install the corrected driver with a single command.

I think the problem also affects FS-1040, FS-1060DN, FS-1020MFP, FS-1120MFP and FS-1125MFP, since they are using the same rastertokpsl program.