Three facts come before any cause. Which stage is this: pre-wetting, Phase I, Phase II, or after release? What is the pattern: the whole mass, one end, the top layer, or the zone beside the door? And what changed: a new straw lot, a different manure supplier, unseasonal rain, a fan that was repaired last week.
Write those three down while the batch is in front of you. A symptom described only as compost is bad cannot be investigated next month, and most compost problems are only understood by comparing several batches.