The report could certainly be clearer here. They don't unambigously say that the table with the primary key was the one rejecting the data, and they do say « W

The report could certainly be clearer here. They don't unambigously say that the table with the primary key was the one rejecting the data, and they do say « We are now extending our test frameworks to include a linter in place for int / bigint foreign key mismatches. » So perhaps the primary key itself was 64 bit, but a column referring to that key in a different table was mistakenly 32 bit.