Don, you gave me a chuckle not because of your choice in heads but because I saw first hand issues related to these heads within the past week. First I mean no offense in telling this. I don`t like the head that you speak of but my preference doesn`t mean beans. You like what you like and there is no accounting for taste. My father was in the small engine repair business for many years and always said he`d sell those heads to those too inept to wind the spool on a bump head.

A dirty bump head can cause problems, be very frustrating if not down right intimidating. I`ve seen people buy new trimmers for the sake of a dirty head. They need to be cleaned regularly in order for the clutch to work as designed. To each their own.
Interestingly enough I fixed an Echo trimmer for the neighbor last Thursday. It had a bad diaphragm in the carb., he said it hadn`t ran since he put it away 2 years ago with the tank full. The diaphragm was not soft but brittle, they just don`t run well this way. It ran great when fixed but had the head that you`re talking about. I put a couple of new twines in the head when I gave it back. He came back over a couple of days later when he had a chance to use it and asked if I had some of those strands for the head of his trimmer. He was surprised when I handed him 5 ft. of .90 twine and a pair of side cut pliers.
My other neighbor who lives right next door to him also had a new Echo trimmer that he said he couldn`t use. He saw me bringing the first neighbors trimmer back and asked me to check his. He said when you bumped the head the twine would retract. His Echo had a spool on it that would clutch in either direction, depending upon orientation and sure enough if you put the spool in upside down it would retract. Both neighbors are now happily using their trimmers. Thought I`d share as this was recent.