The MMC command does not always cut


I am having trouble printing with ZPL code. And I hope somebody can help me with it.
I have set up my ZPL code to print and cut the label.
The MNM command should cut, but with 10% of our labels when send the commands, the zebra printer, print the label but not cut.
We have the Zebra KR403.
I hope any of you can help me!
Thanks in advance.