CD relay has been swapped. Operates as it should. When a call is registered up or down the car will travel slightly then fault, back to normal then fault, intermittently. If the car doesn't make to the landing motor timer faults. Inspection seems to override this this issue. ( maybe it did RCD fault during inspection but definitely not like Normal, I don't recall this comment 100%)
one observation: When I first arrived next day after shutting down the car it took several call with no issue. Almost like things got warmed up and the fault started happening and got worse. Door close LED stays on during travel. Safety Circuit LED goes off during travel when RCD fault occurs. CD relay stays picked during travel and goes off when the car door opens as it should.
I'd swap ribbon cables next. I've had some odd issues in the past from ribbon cables that never move but connection got iffy (especially ecospaces). After swapping ribbon cables I'd run it to see if problem went away or you've ruled that out then move on to checking power at points on board and watching cpu inputs. See if there's any triacs on that circuit on the i/o board too.
Today I noticed a very distinct pattern. The unit would take calls to all landings, when the door reach fully open the controller would RCD fault. When the door reached fully closed the controller would "cycle test" and take the next call with no faults. same RCD fault at all floors when the door reaches fully open. The lock circuit drops and picks up as it should. CD relay energizes as it should. DCL and DOL signal correctly.
The room is excessively humid and hot with summer approaching (no ventilation). I noticed vapor droplets built up inside the relays. Oddly opening the door and working out some heat and humidity the fault stopped happening for multiple calls (not sure if this was a coincidence or effective, TBD)