There is no doubt that such a ship must store spare parts for most things that can break during operation and that everything must be designed so that such spar

There is no doubt that such a ship must store spare parts for most things that can break during operation and that everything must be designed so that such spare parts should be replaceable by robots, after running diagnostics that identify the faults. This is not simple, but it is feasible. It would be feasible much more frequently than currently used, but typically human technicians are cheaper than complex fail-safe automation. Presumably, at least in the beginning, such ships will not be used far from their bases, so they will return there after any defects that cannot be repaired. All essential functions should have enough redundancy so that the ship should be able to return to the base even when only partially operational, e.g. with some engines or propellers disabled.