I don't think 2 rows on the radials are the cause of the problem, but they make it worse than it would have been with 1 row. If it is the fabric
its still the sailmakers problem, he would have seen it on the floor after sewing one section that there was a problem and shouldn't have continued.
Triple step stitching on the headsail UV cover as shown in the photo
is another no-no. More holes and makes it a lot more time consuming to replace the UV cover.
I would be asking for your money
back at this point and starting again with a different sailmaker