New print core issues

[rscudder 0]

Installing a new 0.4 AA print core into S7, no problem very easy, I noticed a little string or something sticking out of the top of the feed tube, didnt remove it and whatever material it was melted and gummed the whole thing up during XY calibration print, cannot get filament to feed down in there now, grabbed another new print core, same little piece of string or something sticking out the top, does anybody know what it is or does it need removed prior to installation? I did a guided core clean with hot and cold pulls using ultimaker cleaning filament, pulled a lot of the purple gunk out of there until it pulled clear, go to run print job and PLA will not feed into the hot end, inspect with flashlight and tube and everything is clear 

Edited Wednesday at 04:56 PM by rscudder
missing extra detail

[alfonsvh 12]

It sounds to me like it's just a piece of filament used during factory QC testing; however that should melt fine...