Ok we have solved this issue for our company and are 95% sure of what the two causes were: It may or may not apply to your situation. We were getting the error every 1/2 hour to 3 hours. Since we did this we have not seen the error in 2 days of printing.   CAUSE 1 (80%) Our Ultimaker 5S is on a counter that is too narrow to allow the dual spool spindle in the back to be used. Therefore, we have separate spools on each side. At first we positioned, each spool on the side