Another step you may want to conside
Anytime the head seperates from the carriage for various reasons it is always a good idea to Reinitialize the Limit Position and Cut down position". This step basically reassures that the cutter/print head are in sync.
I am sure the steps are outlined in your user manual, but briefly turn the sub power off (blue light on front panel). Press and hold Left + Up + Down, and while holding them press the sub power button. This will take you through the steps needed to insure that your system will better serve you.