Greetings from Syncfusion.
We have analysed the issue which you have mentioned. As per the specification of Code128A barcode, it supports only [0-9] [A-Z] and other symbols. Please refer the below UG documentation link for more details,
We have checked with the sample to render the barcode (Code128A) in XAML and code behind, it works fine in our end. Please find the sample for the same from below,
Note: Code128A barcode does not supported the character for lower cases(like “xyz”).
Kindly try the above sample in your end and let us know if it solves the issue.