Before inserting the filament into the machine, always cut the tip. There are two ways you can do that:
- Cut the filament at a 45° angle
- Grab the filament about 10 cm from its end and twist it in a circular motion until it breaks off
The second method is preferable for the Original Prusa MMU2S.
If the filament tip has a blob/head on the end from the previous print, it can cause issues when loading the filament.