DRV8711 - External STALLn / BEMFVn Not Working

I've noticed particularly when I make sudden large increases in torque, with the DRV8711 in external stall mode, the STALLn / BEMFVn output pin used to signal when a valid back EMF measurement is ready remains low and stops responding.  If I then lower the torque, sometimes I can get it to start making active low transitions again.  I'm really curious for any ideas of what could prevent the STALLn / BEMFVn output pin in external stall mode from signalling a valid back EMF measurement is ready.  What actually drives STALLn / BEMFVn output pin active low?  Is it just a counter or is there additional logic that could be susceptible to electrical noise from current surges?  Could the counter get corrupted?  Or maybe is it possible the back EMF signal could somehow cause the STALLn / BEMFVn output pin to malfunction?