We show that for all integers $m \geqslant 4$ there exists a $2m\times 2m\times m$ latin cuboid that cannot be completed to a $2m\times 2m\times 2m$ latin cube. We also show that for all even $m>2$ there exists a $(2m{-}1)\times(2m{-}1)\times(m{-}1)$ latin cuboid that cannot be extended to any $(2m{-}1)\times(2m{-}1)\times m$ latin cuboid.