Hmm. I have never had that except when the printer is faulty, or it has memory corruption. You could try fully clearing the machine first. Otherwise it could be more serious.
Here is the clearing procedure. NOTE: YOU WILL LOSE ALL DATA, so make sure you have done your reports etc first.
Look under the paper rolls, and you should see a little battery cover. Open the cover, and there should be three batteries inside. remove just one battery.
Turn power off at wall.
Turn key to REG mode.
Wait about a minute, then turn power on at wall. After a few seconds, you should hear three beeps.
Put the battery back in.
Try the machine now, and see if the print problem still exists.
If you need more help, I am 'NZtech' at www.Eposwizard.co.uk just go there and send me a message.
Mark
May 2008