I have been printing with my new sv06 for a couple of weeks now, and had some issues with pla, so switched to petg, and have been getting excellent results from transparent coloured petg, and wanted to see how the printer would works with tpu ( that does work well in my MANY other printers) but every time I loaded the tpu it would just scrunch up inside the extruder and not reach the hot-end. this behavior upset me, so I decided to dismantle the entire hot-end extruder assembly, what I found concerned me ie a length of pale blue(about 5mm long) filament in the planetary gear box, the primary filament drive gear loose on the drive shaft(both rotationally and positionally) and the wire cable for the bed sensor being very close to the hot-end.
my opinion as to where these defects were sourced is during manufacture.
upon tightening the drive gear, removing the plastic from the gearbox and re-assembling the entire hotend I then tried the same roll of sainsmart tpu, and while it did prime this time, when I attempted a print the extruder again stopped extruding and when attempting to unload it would not, and also the filament BROKE from the force I was applying while trying to manual unload, and upon dis-assembly the filament was SCRUNCHED up inside the extruder housing. the only times that I have seen this behavior with flexible filaments is when the feed path has a large (larger that 0.3mm) gap between the output side of the drive gear and the feed path to the hotend.
while the hotend assembly was off the printer for the second time, I decided to do a visual inspection of the visible sections of the wiring and could see that the brown wire of the three wires attached to the bed sensor had mostly separated from the crimp fitting in the plug, and no other wires showed any similar effect, just the one wire only
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I had similar issues with TPU getting scrunched up in the extruder gears, also happened with cleaning filament. Both are soft flexible filament. I unscrewed the pin with the spring to clean it out. Readjusting the spring tension helped a bit, but it seems the extruder is susceptible to this issue. I’m extra careful when loading soft filament now and manually turn the wheel forward until I can feel the filament being grabbed and moved forward before I press the button to continue…