I have come across a case when DBDSDC returns U and VT outputs that are not quite orthogonal in LAPACK 3.3.0. See the attached test program.
For this particular matrix in the test, UT*U has elements in the order of 1e-9. I am expecting if U is orthogonal, UT*U should be at round-off level, in the order of 1e-16.
Note this behavior is only seen in LAPACK 3.3.0. In LAPACK 3.2, DBDSDC returns INFO>0 as it fails to converge.