the boogers on the thread may be causing the issue.
a thread file or a small 60* triangle file may be lightly employed to improve any high spots
you could add some ink from a sharpie pen to the spindle and try to see where the interference lies
a thread file or a small 60* triangle file may be lightly employed to improve any high spots
you could add some ink from a sharpie pen to the spindle and try to see where the interference lies