first insert works, second doesn't even though only a light difference

[Fou-Lu]

So let me get this straight.
The primary key increases regardless of whether the record inserts? You better verify with the SQL guys, that sounds an awful lot to me like a corruption in the datafiles if that's the case.
Your code is irrelevant. Since the query will execute with no changes successfully and no error from a client, this tells me something else is broken server side.