I don't think residual air in the system would lead to fluid loss, this is only possible if it leaks out somewhere (which could be where the air is getting in). Air not removed during bleeding a system with no leaks would lead to the compressible air making the brakes feel soft. this air could be anywhere in the system and may sometimes be more noticeable than others depending on where it is and whether it is in the form of. bubbles or micro bubbles spread throughout the fluid.
Some cars are notoriously hard to bleed and the Morgan CX may just be one of them
