All the extruders shown in this post
viewtopic.php?f=16&t=3484 are "Wade's" or "Geared" extruders - meaning that there is gear reduction between the motor and the hobbed bolt. If you have a Plus, you probably have a geared extruder. The picture of the extruder in this post
viewtopic.php?f=74&t=5202&p=47618&hilit=alu#p49745 shows an aluminum "direct drive" extruder.
The aluminum direct drive extruder conducts heat from the motor to the driving point, so the filament gets warmed up, which softens it. Many people have added fans and heatsinks to their motors to reduce the heat being transmitted to the filament.
Once the filament leaves the "pinch point" between the hobbed bolt and the idler wheel, it may need some support to stay straight until it enters the throat of the Ubis (or other Hot End). This is called the "drinking straw" solution, although in reality people use PTFE or metal tubing. Here's how one person did it
viewtopic.php?f=19&t=4968&p=32936#p32936Another thing to try is active cooling. Mount a fan that blows air at the zone in question. If heat is rising up from the melting zone and softening the filament in the gap between the pinch point and the Ubis entry, the fan will reduce that heat dramatically.