There was a Red Texas that was not fertile till it beame 2 years old from one hobbyist I know of..
Then there was a faded red texas that was around that age too and he bred 9 times with no success. The 10th time he made wigglers. The owner just had them together and left them there and not worry about him fertile or not and he got to try many times as he aged.
So to confirm a fish to be infertile is not as simple as breeding him a couple times in his early stage of life.
And when they hit one, doesnt mean they will always hit after. So in fishes like that, dont take fry for granted.