Summary When the filament is blocked due to unrolling problems on the reel, the printed is often destroyed. To prevent this to happen, I made a switch that switches the printer into "PAUSE"-mode, until I have solved the problem. In Marlin there is already something prepared for the "Filament Runout Sensor". After pressing the "RESUME"-button the printing proces gets on at the latest point. See attached Word document. RepRapWorld helped to make the changes in Marlin and get the thing working. Thanks! See also the working at: https://www.youtube.com/watch?v=2THpOezBavQ