Overlocker machine janome harmony 9102d

Question

I have spent hours threading and re-threading the machine according to the diagrams in my manual, but can't seem to correct the problem. It is so weird because everything will start off fine and all of a sudden the threads stop locking and when I open the machine the lower looper thread has somehow escaped the eye of the looper--it is still correctly threaded everywhere else and the thread has not been broken (so one end is wound around the thread cone and the other is still locked up in my stitches but somehow the middle has escaped a seemingly solid metal looper--I can't understand how this is physically possible?...)