Are there any red LED lights flashing anywhere? If there are, count the number of flashes between the longer pauses. I don't have an XM-3150, but a lot of scooters have built-in diagnostic codes that can help identify the problem.
Does the motor *thunk* only once per power cycle? Like, you turn the throttle, it makes the noise, and then you can't get it to do it again until your turn the controller off and then back on?
I think the XM-3150 has a circuit breaker, right? Make sure it isn't tripped.
If that doesn't solve it, elevate the rear wheel off the ground. With the scooter off, turn the wheel by hand. Does it spin relatively freely? Let us know if you feel any vibration-like feedback. Next, turn the scooter on and twist the throttle so that you hear the thunk, and with the throttle engaged, try turning the wheel by hand. Does it still spin freely, or is it locked into place? Again, let us know the result and we'll have a better understanding of what's going on.
Another thought: sometimes with a crash a wiring harness will become loose. The throttle signal actually passes through two connectors before reaching the controller. Once up front by the handle bars, and a second connector closer to the controller. Did the throttle wires get crushed in the accident?
Also, check the wiring harnesses between the motor and controller. There should two sets of colored wires (yellow, blue, green), thin ones and thick ones. The thick ones are what power the motor. The thin ones are what tells the controller the rotational position of the motor. Examine the thin wires' harness.