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Instead of a label, the printer produces lines of raw characters — often right after a calibration run. Two very different causes share this symptom, and the printout itself tells you which one you have.
If you can recognise your own data in the output — the ZPL commands themselves printed as text, carets and tildes included — that is almost always dump mode: a diagnostic state in which the printer prints the bytes it receives instead of interpreting them. It is easy to trip accidentally during a feed-button sequence, which is why it so often follows calibration.
Leaving it: power-cycle the printer. If it comes back dumping, send
^XA^JR^XZ — or power-cycle while not holding
feed.
If the output is not readable echoes of your file but truly garbled characters, the other candidate is that the printer does not speak the language of the file. Older desktop generations are EPL printers, and feeding ZPL to an EPL interpreter produces exactly this half-digested output. Checking which language your file actually is takes a second with the printer language detector — and rules that half in or out.
The two fixes share nothing: dump mode ends with a reset and no file changes; a language mismatch ends with converting the job or re-targeting the printer, and no number of resets helps. A minute spent reading the printout picks the right path — and an old printer that "went crazy" after calibration usually just needs the first one.
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