Code128 barcode encoding in reporting module

Hello,
I'm trying to include a code128 barcode in a report, reproducing a barcode provided by our costumer, however it looks different.
After some attempts I found out that if the datakey is composed by an even number of digits, the barcode pattern created in the reporting module is different with respect to barcode generated using online generators. With an odd number of digits, they are equal.
My guess is that the encoding in the reporting module is switching between code a/b to code c.

Does anyone know which encoding is used or if I can force to use one?

Thank you in advance for your help.

You might be able to get somewhere using something like the approach here?