The Zebra thermal printers are low maintenance, keeping the printer and printhead clean should be enough.
We also recommend that you unplug the printer in case there should be a thunder/lightning storm, the print adapters are sensitive to electrical surges.
Troubleshooting the Zebra GK420d
The first step of troubleshooting Zebra printers are to restart both the printer and Consignor.
This especially if some fonts are missing or are weird, because Consignor sends a font package at first print.
Sometimes the GK420d can swap between line/page mode, the labels can start look something like the example below.
This can be caused by a poor connection between the powercable and the power adapter, ensure that the cables are correctly connected.
Restart Consignor, then the printer to solve this issue.
Sometimes the printer needs to be calibrated - see example below.
To calibrate the printer hold down the feed button untill the status LED has flashed green first once and then twice - then release the feed button.
You can also do calibration with the Zebra Setup Utilities