DataMatrix with strict requirements

Hello...thanks in advance to anyone who can help me.

I need to draw a DM with ModuleSize=0.4807692307, Symbolsize=52x52 (opt n. 21) to encode an ASCII string of 256 bytes (see Codice below): the requirements are mandatory to comply with a new kind of italian payment system. I'm testing with the code below:

Codice:='codfase=NBPA;183002128500000001221200000000136210000000001138961P100222610289RSCSNT70C65L407LRESCUADELLI SIMONETTA                   FATTURA N. 9999970 DEL 11-10-2021 TEST EMISSIONE                                                                          A';

QPDFile.DrawDataMatrixSymbol(170,52,0.4807692307,Codice,1,21,0);

DrawDataMatrixSymbol returns 1, the barcode is visible but the content is incomplete (the last 13 chars are missing '            A'). Changing the "blanks" with "zeros" solves the issue, and also setting the symbolsize to zer,  but i cannot use the "tricks" in production.

It seems to me that the "automatic" C40 encoding is "broken".

I've also tried to encode the same string with online tools andthe result is perfect.

Any idea on how to solve the issue ?