These requests begin with stored tables, so a query that looks correct on a fresh build can still leave the wrong result. Read what already exists and which source change occurs before your command. Some tasks need a batch repair. Others need a full rebuild because the required key no longer reaches normal replacement.
Keep the model grain explicit while you work. A partial subscription batch can remove an unrelated subscription when it matches on user_id.
An empty target makes MAX return NULL. An undated arrival can append forever if you include it as new on every run.
You'll also revisit the deterministic tie-breaker, a missing replacement key, and an inclusion-rule change. Every result is checked after execution and replay against the requested current source state, including older rows and missing business values.