I have something like that on my Stihl.
You cut a piece of line(about 12-15 inches long), feed it through and put the middle behind a tab to hold it. That tab on mine is stiff!! and a pain in the butt.
Don't know how that one you showed holds the line.
It also takes those thick plastic saw blade looking things.
It wastes a little line as there is about 4-8 inches left when you change line.
Hi, I use these heads extensively, found the same problem, the cam inside would get sticky and not hold string in place very well. My cure for the problem was to get some anti-seize lubricant and take the cam apart, pull the shaft to it out, grease it up with the anti-seize and put back together. No problems since, I do it now automaitcally to any new units I use before even sending them out on equipment and we never have the problem again. Hope this helps