Exact same problem on my Pedicab with one month old 901 front hub using the Golden Lithium Battery 36V16A. Tried two different Anderson connectors, but problem remains.
Specifically, on start (even without load) motor cuts out if throttle is opened quickly. After about five seconds will work if throttle is opened very gradually.
Once in motion, motor cuts out under load (hills) at low speed. After about five seconds it will work if load is decreased either by peddling hard first or changing gradient.