Dimming Lights

I recently bought a house with an IN-Law attachment tapped into my power source. The in-law has a seperate breaker box with mcb\\\'s. Recently I noticed the lights dimming and a clicking noise in the breaker box. Upon c;ose examination, I noticed electricity arching over to the next MCB. What does this mean and how should I fix the problem?

it sounds like there is something there for the electricity to start arcing over in the first place, switch off all the incoming electricity and look (dont touch)

or it could be something is breaking down, but as you are in America, it may be against your regulations to touch it, best call an electrican to have a look to give a scond opinion