The guide rods/rails upon which the cutting head assembly rides need to be kept free of cutting debris. They should be wiped or blown off before carving a project, and wiped occasionally with a thin coat of light oil for lubrication.  If the rails are allowed to accumulate dust and debris, the machine will halt during usage and an error message will be seen on the display with a reminder to clean the rails.  Once they have been cleaned, pressing the ENTER key on the keypad will resume operation.