In compactifications of string theory, to preserve supersymmetry often branes need to wrap subspaces that are specified by holomorphic equations in the compactification space $X$. Additionally there exist complex structure deformations of $X$, which are often massless unless lifted by extra effects. These complex structure deformations alter which subspaces can be specified holomorphically, 'shifting the sand' underneath the branes. Hence to continue to preserve supersymmetry under a complex structure deformation, we must shift the branes together with the deformation, to track holomorphic subspaces.
But is this always possible? That is, are there cases where a brane locus cannot be continuously deformed to remain holomorphic under a complex structure deformation? I have not been able to find such examples in the literature. I would be grateful for a reference, or to hear a reason why such examples cannot occur.