I had a circuit fail and trip breakers with no load, what could cause that?
The issue turned out to be rodent damage.  To diagnose, I plugged the freezer into a different circuit and it worked fine. The breaker tripped again, no load on the circuit.  Also, other electrical problems. Another circuit was failing.   As we all know, failures of cables inside walls is extremely rare. Usually somebody has drilled through one or nailed it.    I traced it down by pulling switches and outlets and testing for continuity and shorts between them. I pulled off some sheetrock and found a dead mouse in the wall and the cable chewed through.
A couple of times here I've mentioned potential rodent damage for electrical problems. It's real and have personally experienced it. It's hard to find and sometimes, even harder to fix in inaccessible areas like vaulted ceilings.