Start here — before replacing any parts
Remove the physical jam before recalibration; do not pull hard against a closed printhead.
Confirm the XP-420B hardware interface and the paper/sensor type in your printer.
Manual scope: Check media sensor type and cutter revision
Do these checks in order
Follow the steps below and keep a record of what changes after each one. Stop when an actual cause is confirmed.
Turn the printer off and allow the printhead to cool. Open the printhead cover with the normal latch; remove scraps or adhesive without scraping the printhead.
Reload labels as shown in the XP-420B media-path diagram, between guides and over the roller, and close the cover securely.
In Diagnostic Tool, set the actual label dimensions and choose Gap/Black Mark/Continuous based on your roll. Run sensor calibration.
Press FEED in normal standby: observe whether exactly the intended amount advances without skewing, then print a simple test label.
If the problem is gone
Labels feed evenly and a test print finishes: the obstruction or media configuration caused the jam.
If the problem is still there
Media bends or jams again at the same position: examine guides, roller and optional cutter path for damage; avoid forcing the mechanism.
Which cause matches your result?
Use these more specific checks only when the earlier steps point to that possibility.
01Media sensor does not match installed labels
Compare media type with printer and driver configuration.
Run the correct sensor calibration procedure.
02Label dimensions are set incorrectly
Check the configured width and height against the installed label roll.
Set the correct label dimensions and retry.
03Label material is physically trapped
With power off, inspect the media path for labels or adhesive buildup.
Remove the jam and clean affected feed-path areas as documented.
How can I tell it is actually fixed?
Run several consecutive feed/test-print cycles and confirm no renewed red flashing/jam.
Before buying a replacement part
If a cutter or roller is damaged, confirm that optional module’s exact part version.
Where this guidance comes from
Primary reference: View the manufacturer or manual reference ↗
Applicability: Check media sensor type and cutter revision. Source evidence: Manufacturer/manual-supported; question demand not quantified.
The instructions are original English troubleshooting explanations derived from the listed technical facts; they are not a verbatim service manual. Do not apply them to an unverified revision.