State: stopped "Filter failed" on a Xerox Phaser 6125N. how do you troubleshoot a printer in Linux?

[Albretch Mueller <lbrtchx@gmail.com>]

 I got a:

_OFL="hwinfo_$(date +%Y%m%d%H%M%S)_hwinfo_printer.log"

hwinfo --printer --log "${_OFL}" 2>&1

17: USB 00.0: 10900 Printer
  [Created at usb.122]
  Unique ID: L0iK.+dt1oXx0UKE
  Old Unique ID: vxkL.pGWWNSDBYN7
  Parent ID: 2UT6.DFkaVl_rzX0
  SysFS ID: /devices/pci0000:00/0000:00:12.2/usb1/1-3/1-3.2/1-3.2:1.0
  SysFS BusID: 1-3.2:1.0
  Hardware Class: printer
  HW Class List: printer, usb
  Model: "Xerox Phaser 6125N"
  Hotplug: USB
  Vendor: usb 0x0924 "Xerox"
  Device: usb 0x3d61 "Phaser 6125N"
  Revision: "1.00"
  Serial ID: "LAL056826"
  Driver: "usblp"
  Driver Modules: "usblp"
  Main Driver Module: "usblp"
  Speed: 480 Mbps
  Module Alias: "usb:v0924p3D61d0100dc00dsc00dp00ic07isc01ip02in00"
  Driver Info #0:
    Driver Status: usblp is active
    Driver Activation Cmd: "modprobe usblp"
    Driver DB0: 2, usblp
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #13 (Hub)
~
 and after mostly following the steps outlined in:

 https://rickvanderzwet.nl/trac/personal/wiki/XeroxPhaser6125N

 https://wiki.archlinux.org/index.php/CUPS/Printer-specific_problems

 I can see the printer fine both while using cups going: localhost:631
and in libreoffice and okular, but the printer doesn't actually print.
The message that I see in cups is: State: stopped "Filter failed"
~
 A google search a less than 5 sinvoll hits which weren't really helpful.

 WOuld you suggest a good guideline about how to troubleshoot printers?

 lbrtchx