UM5 Pro - Material Station Filament Not Releasing from spool

[bvsengineering 1]

I've run into a recent issue in which the end of the filament on our filament spool did not come free from the spool a the end of the print.  This caused the print to fault out, with ER62 ("Filament Sensor Error").  I had to manually pull the filament out of the material station and then cycle the printer power to clear this error.  After inspection, I discovered that a notch had been ground into the filament, due to it being stuck on the spool and the pre-feeder continuously attempting to feed it.  Once the notch was ground in, it couldn't have been retracted by the pre-feeder, as there was no material left at the pre-feed gears.  I had trimmed the filament end flush to the inside of the spool, but it apparently still wedged in the triangular opening (ColorFabb spools) and failed to dislodge.

 

1. To minimize this issue and improve the chance of an automatic recovery; Could a software update be implemented to assume the material spool is empty if the pre-feeder feeds a certain number of steps (or time, if not using steppers), and then automatically acts the same as if the material sensor detected a filament run-out.  
2. How can I open the pre-feeder to clean out any debris from it grinding of the filament.
3. Can there be an option configured to automatically switch to the 2nd head, if I have the same material and print core loaded for it and the material station pre-feeder faults for head #1?  This would allow it to continue, even if the material station encounters a jam for position 1.

 

 

 

[Bundle 1]

We have 2 bundles.  the material station on one is going back for service with an inoperative prefeeder caused by grinding after a PVA jam.  The jam was cleared, but apparently the prefeeder clogged up and there is not adequate tension for the prefeeder  to complete the feed.  After the filament slips a bit it errors out.  There does not appear to be a way for the user to service the prefeeder which means every time this occurs, it needs to be shipped back for service.  is there a user procedure to clean the prefeeder? Having a device prone to PVA jams/breaks which cannot be serviced on site is very suboptimal.