Zinsco Burn-a-Buss........The Zinsco Breaker has a poor connection to the buss bar......They're both a light alloy/aluminum and just touch each other....Not fit in a hole or snap on a copper buss........as the connection weakens they snap crackle and sizzle and finally start on fire....Have a LOOK at the BUSS....
Inspection by a licensed electrician is the safest option.
And if You think that's offensive....."Ever hear the one about the LAWYER and the REALTOR.............................."