printing

Missing label when print directly from application form C#.net(No often)

I'm developer. I develop an application windows service to print label from my template(pdf file) through printer name method(TCP/IP).
I am using Zebra Zt410 printer with version V75.20.14z.
I will set given quantity then printer automatic print with exactly quantity but sometime, we miss one or more label.
I check log in queue printer spooler. It still match quantity with given quantity but Zebra printer still miss label.
I don't know why missing label in printer and please let me know how to prevent it happen again!

Thank you so much.