You're right, it doesnt always work, in fact, I've never been able to make that work. but here's what DOES work.
turn off all the power, printer and material station both. open the feed on the station the material is in. open the material station, cut and remover the spool of the offending material. remove the clamp on the print core and put the bowden tube out. now carefully and slowly pull the material out from the bowden tube until it clears the entire material path. take the cover off the feeder to assure it;s clean. turn the powers back on and assure that the printer knows the build surface has been cleared.. you may have to select "change material" so the printer will be ready to reload. and at that point you can reload the material
I agree, the firmware really needs both to allow all this easily, AND to allow purging the printcore independently so one can tell if the core is good without all the cold pull, hot pull, cleaner filmament mumbo jumbo Maybe it's too much for those netherland engineers to grasp?