I am sure this is not new. I was having some trouble with my metal nose hackle pliers. If the two pieces didn't lay flat or meet perfectly, the hackle would slip out. I also would sometimes cut the hackle with the nose of the pliers.

Solution: I put about 1/8" to 3/16" shrink tube on each piece. This allowed for error in the tips not matching perfectly as well as expanded the gripping surface.

I don't know if this will help any one else but it sure kept me from throwing a dandy of a tantrum.