Thanks for the suggestions.
I am using the default DAZ shaders, opacity set to 100%.
There is no grey pixels at the top of the transmap for the hair.
I did a render with the rate set to 0.1 as you suggested, the lines almost disappear but not quite.
It would be good to get rid of them but even with them the hair is still usable, whether the lines are noticeable depends on the colour of the hair and the background and how close up you are to the hair in the image.
Of course if you know they are there you can see them, but ...
Attached is a render with standard shader settings to show they still look OK.
Click thumbnail to see full-size image