Edit: the original model has updated to 3.1 which now includes a similar rubber band option, therefore just use the original no need to use this remix, unless it did not work well for you. (e.g. you have a longer rubber band)
This version use only rubber bands, no spring requeired.
The following 2 parts are different, the others are the same.
As shown in the picture below, use a rubber band (red) to connect the 2 hooks at the ends of the Push Action (blue) pins, and guide it to sit above, in the middle slot of the Midplate (yellow). Make the rubber band a propper length, so it is already a little tight when the Push Action is in the up postion.



The author remixed this model.
This version use only rubber bands, no spring requeired.