(But please only do maintenance on the machine if you are an owner!)
It's a common problem that someone might twist the e-stop too hard. It's a quick fix to just re-instate the stop into its casing.
Removing the electrical box - make sure power is off before doing this
Removing the back of the electrical box to expose the e-stop
This grey piece holds the e-stop in position - the e-stop (on the left) twists into place and then the screws on the grey piece need to be tightened.