If the needle is going down but not picking up the thread, the first thing to do is clean the bobbin area and try a new needle. If that doesn't help, it's likely that you are pulling on the fabric and deflecting the needle so that it isn't positioned correctly to make the stitch. It's not really the fault of the BSR, but of free motion quilting in general. (You can prove or disprove that statement by trying free motion without the BSR engaged and see if you have the same problem.)