Multiple possibles here..
no 1 look at the design is there something in the stitches in that area that cause the thread to skip.
No 2 is this a spot in the design where the machine changes sewing speed ?
No 3 your hooping
no 4 hook timing
no 5 tensions combined with hook timing and hooping.
I think I see the stitches starting to go south a few stitches before the missed stitches. Also I see the same thing kind of starting in the little bit of the design I can see to the right in the picture. I would start by adding some additional tension in your bobbin and matching up the top thread. Do have a way to measure bobbin tension? Do you know how to drop test bobbin tension ?
reference
https://www.google.com/search?client=opera&q=drop+test+bobbin+tension&sourceid=opera&ie=UTF-8&oe=UTF-8Some additional details would be helpful....multi head Y / N
sewing speed
needle size
machine brand
do you use needle plates for sewing hats....
mikemoose