Open shed problem

I have 4 threads that are in the middle of my shed that need to be cleared so weaving can begin. They appear to be from the bottom of the cross. I checked the heddles and found no cross over of threads and the reed is sleyed correctly, but I can't clear this problem to start weaving. I have notice that I have a few more bottom threads in a row in this area without a top cross thread between them from a broken thread. Any suggestion on what else to check to clear this problem would be helpful. Thanks TNWEAVE