Stihl String Trimmer - FS-KM - Lose Nylon Lines Back into Mowing Head

[toneil44]

After only a few minutes of trimming operation I typically lose both nylon lines back into the mowing head. I then take off the top of the mowing head to feed both lines out of the mowing head to resume trimming only to lose the lines back into the mowing head again.

What am I doing wrong?

 

[The Lorax]

Are the eyelets still in place and not sharp?
Trimmer line gone brittle? Try some fresh stuff or soak the line in water for 24 hrs and try it then.
Also trimming close to wire and hard surfaces will wear the line down quickly even snapping it.

 

[DND 9000]

You turned the mowing line onto the spool the wrong direction.