It tripped again, but now I've identified the roof breaker. I should have switched that off when I moved in, as the roof isn't mine.
I wonder how it can trip the 64A main breaker without tripping the 30A roof breaker.
Also, holy hell, 64A? This is just an apartment, my parents have like 20A or 25A for their two-floor house with garage and stuff. Here we have 30A just for the bedroom. 😲