As the printer uses direct thermal (heat) technology, the inside of the machine can become too hot to print. When the temperature gets too high, the machine pauses printing to give the machine chance to cool down. While paused, the power lamp of the printer flashes in orange slowly, and at the same time you will see a dialog box as shown below, informing you that the printer is cooling. (The dialog box may be slightly different in each models.)
Once the temperature has dropped sufficiently, printing will resume automatically.