How would I know when a reverse switch is bad?

I turn on my car and my gear is not in reverse but the reverse lights are on. I told dad to hop in and put it in reverse, so he did and I saw when he get ready to go in gear, it shuts off. Then when the gear is in fully, it comes back on.

Could it be the switch bad or sticky?

 

Yes, the switch could stick in place. Do you put it in reverse when you park it?

 

The car stay still, it not running yet. So, I turn the key on and the reverse light is on without the reverse gear in. I get my dad hop in and press in the clutch and put it in reverse, it goes out when it slides in then back on when it fully in gear.

 

bump