The Knill-Laflamme condition for a stabilizer $\mathcal{M}$ is
An error with Kraus operators $\{E_k\}$ is correctable if either $$E^\dagger_kE_l\in\mathcal{M}\quad\forall\, k,l $$ or there exists $M\in\mathcal{M}$ such that $$\{M,E_k^\dagger E_k\}=0\quad\forall \,k $$
But consider a unitary error $U$, then $U^\dagger U=I\in \mathcal{M}$. Does this mean that all unitary errors are always correctable by any stabilizer? It shouldn't, because for example Shor's code doesn't correct double bit flips. What am I missing?