Line size doesn't affect the reel. That is just what the Manufacturer recommends and it fills the spool correctly and the correct amount of recommended yards of line.
I use 8,10,17,20, and there is no difference other than the speed of the retreive due to the size of the spool increasing as you reel in different size lines.
Hopefuly you just got a bad batch and the NEW one will do better for you.