The big red stop buttons are wires to the main power line and they lock closed when pressed so they can’t ge easily opened again by accident.
For the other switches stop/hold/resume such as those on the pendant they should be momentary buttons. Pressing the buttons sends the pin HI on the arduino and the software stops everything. After a stop you need to type into the computer to resume and tell it everything is alright. The feed hold is also momentary, again triggering the soft ware to pause. I assume the stop on the pendant is a feed hold. After a feed hold you can resume again with just a press of the resume button. Resume again momentary. The buttons really just send a brief signal for the software to interpret.