I have worked it a couple different ways. More so when the dog is spinning but might work for this too.
1) Dog comes in the blind with lead on and the helper carefully grabs the leash to hold dog in position. Make sence? I had to see it to understand thats why I ask.
2) A back door blind. If the dog starts to spin or take eyes off helper, the helper runs out the back door. Dogs reaction of "oh crap where did he go". I better not move or he will get away.
Also maybe handler conflict or caused by doing call outs all the time?