The rendering of isc_formatted_exception by Jaybird is wrong: it repeats the exception parameters as if they are not part of the rendered exception:

For example:

CREATE EXCEPTION ex1
  'something wrong in @1@2@3@4@5@6@7@8@9@10@11';

EXECUTE BLOCK AS
BEGIN
  EXCEPTION ex1 USING ( 'a' , 'b' , 'c' , 'd' , 'e' , 'f' , 'g' , 'h' , 'i' );
END

Executing this results in error:

exception 1; EX1; something wrong in abcdefghia0a1; a; b; c; d; e; f; g; h; i; At block line: 3, col: 3 [SQLState:HY000, ISC error code:335544517]

Instead, it should result in:

exception 1; EX1; something wrong in abcdefghia0a1; At block line: 3, col: 3 [SQLState:HY000, ISC error code:335544517]