In some cases, when running GET _transform/_all or through kibana UI (management/data/transform), it shows some transforms are thrown errors:
Found task for transform [...], but no configuration for it. To delete this transform use DELETE with force=true.,

However, it could be wrong and false positive, when you run GET _transform/<transform id> or GET _transform/<transform id>/_stats for the problematic transform, the stats was in green health, and the documents_processed counts are increasing.

We need to figure out what could cause this problem.