Normally it breaks from pressing the roller at the bottom.
The switch is at the top of the roller, so just to let others know,
always press at the top
Being 6 years old Dog, i'm guessing yours is just wear and tear

There use to be a place that made metal replacements.
But they are easy to fix.
If its thr little axle that spins inside the momentary switch. You can just drill it out, and replace with a cut off from and old allen key.