Sometimes you just gotta take a broader view
Database pilot fish is about to leave work when a co-worker catches him as he's walking out of his cubicle.
"He says that he and another colleague found an issue with a table that's not inserting unique IDs -- the primary key -- for records." says fish. "And it's a table I remodeled a few years back."
That means it's probably fish's fault if there's an issue. But fish is also intrigued by the problem -- after all, it's unlikely that SQL Server would fail completely by inserting the same IDs.
So they go to the co-worker's desk, where SQL Server Management Studio is on his screen, showing a table containing about 150 records. Sure enough, toward the end of the table is a bunch of records all showing an ID of 1 instead of a unique ID.