Problem when printing with linkos

Hi everyone.

I'm developing a Windows application in WPF, which uses the "link-os" SKD to print a large amount of tickets over a USB connection with a GC420t. The latest problem, and this is what makes me lose sleep at night, is that during printing, the printer apparently loses the detection of the mark (or gap) and begins to print the content in a wrong position relative to the top of the ticket.

Important points:

- My software build a ZPL string in runtime and sends it to the printer;

- I'm using the "GC420t" driver (non EPL);

- The printer properties are correctly assigned: label size, media type, speed, darkness, etc;

- The printer is calibrated.

Below, attached ZPL sample code, and the link to a video that demonstrates exactly the moment the error happens. Every help is welcome. Thank you very much.

Zebra GC420t error while printing - YouTube

ZPL Sample code attached.