My first thought is that the load is back driving the motor. This may be the case if the helix angle and coefficient of friction combination means that the worm drive is not self locking.
To test this, can you turn somehow safely apply the load to the system without the motor connected to see...
I believe that your design is referring to a planetary gear system with a sun driving a double level planet which in turn drives 2 internal gears.<br><br>Our company produces Excel based design software which can be used to calculate the resulting forces in your mesh. Alternatively...