Solution for the front of the extruder
Insert the flexible filament directly into the extruder.
If possible, the recommendation is to Insert the filament directly into the extruder (direct extrusion printers), thus avoiding the use of filament guide tubes (extrusion tube or Bowden type printers). These tubes cause high friction on the flexible filament causing several issues.
But, if, on the other hand, you have no choice and you use this type of tube, make sure that they are made of PTFE (Teflon) material. Pneumatic or silicone tubes are not optimal. Also, make sure to eliminate any bends or kinks that the tube may have by trying to make it as straight as possible to avoid unnecessary friction.