If it's condo then most likely it's leakage to ground with high resistance as your normal peak usage doesn't induce high enough leakage current to trip the RCCB. Could be wet damaged wire insulation or neutral wire get damaged by mounting stud/bolt/screw and leak directly to concrete and not via earth wiring. Get experience electrician that know use the right tools (leakage current clamp meter + insulation tester) to troubleshoot this. There is 1 infamous kiasu self-proclaimed "electrical expert" that don't know how to make use of his tools (ground/leakage clamp meter & multifunction tester) except flaunting it when troubleshoot RCCB tripping, and still have the audacity to charge half assed inspection 600+.


If for some reason you unable to replace the wiring and just repair the damaged insulation, you can try isolate the circuit into it's own 16A/20A RCBO and not downstream of your existing RCCB.