Above 72 per cent at spawning, DMR reports that aeration fails, anaerobic conditions can kill the mushroom mycelium, and brown and white plaster moulds appear. Wet compost is also heavy and packs down, which blocks the air a blower is paid to deliver.
Dry compost fails the other way. NHB, reproducing ICAR guidance, links compost below 64 per cent moisture, under a wet casing layer, to weeper mushrooms. Correct water at a turning, where it can be mixed in, rather than pouring it on a filled bed later. Both faults cost the crop, and both are cheaper to prevent than to repair.