I'm having a problem with my Ultimaker Original, which has been working fine for 2+ years until now. Whenever I try to print I end up with either no extrusion or varied extrusion of PLA (i.e. extrudes well in some places, extrudes very little in other places, or no extrusion at all), even though I've check that the print bed is level. I've noticed that the Bowden tube is also jumping and separating from the hot end isolator coupler. I've an extrusion clip on both the hot end and the motor end of the Bowden tube which have worked well up until now. There are some 'bite' marks on the Bowden tube at the hot end and I'm unsure how they would have got there as my prints have not been getting worse over time (until today). There is no blockage of the nozzle as I've removed it and clean it completely and the printer can extrude when idle (i.e. when hot but not set to print). What can I do??? Any suggestions would be great!