This text block overflows. ^FB does not truncate — Zebra: "Text exceeding the maximum number of lines overwrites the last line." You get an unreadable black smear on the final line.
Increase the line count, shorten the text, or reduce the font size.
^XA^FO50,50^FB400,2,0,L^A0N,30,30^FDone two three four five six seven eight nine ten^FS^XZ
^FB content exceeding the declared maximum number of lines.
Neither ^PW nor ^LL is set. Both fall back to a value stored in the individual printer, not to a value in the spec — so the same ZPL prints differently on two printers of the same model.
Set ^PW and ^LL explicitly in every format.
This example does not currently trip DT-03 under the default 203 dpi GS1 profile. That is worth knowing rather than hiding — see the open items in the repository.