MSAN error

The following code snippet encounters an MSAN error during execution:

 positions.col(i) =
        (positions.col(i).cast<float>().cwiseProduct(bbox.sizes()) +
         bbox.min())
            .cast<double>();

Error message:

Error looks like: MemorySanitizer: use-of-uninitialized-value
 third_party/eigen3/Eigen/src/Core/arch/AVX/PacketMath.h:930:3 in float vector[8]
 Eigen::internal::pmul<float vector[8]>(float vector[8] const&, float vector[8] const&)

The code works fine if the temporary positions.col(i).cast<float>() is converted to a stack variable.