same here - the ranking does not work properly.

However my main issue with recycling used material is that the heating and cooling process used in 3d printing changes the crystalling structure of the materials and many of them would not be suitable for a simple melt and extrude process.
So quiote probably specific thermal cycle would need to be used.
On top of that you would need to wash the old filament to get it totally clean and grease and dirt free before re-extruding.

I'm not sure how easiyl you would be able to fit everything needed into a single desktop unit.

I've seen and played with the last three filament extruders that were marketed and died a death.

At the moment i just don't see it as a process that can be easily reduced to a small cheap, desk top unit.

As far as the percentage of failed prints - it's less than 1 %.

Once you have the prnter dialled in and a good print surface - print failures should not be a 'thing'.