Some vertices stopped moving in sculpt mode On a project I was working on creating shape keys and sculpting the model for those keys, suddenly while attempting to create a new shape key some of the vertices of the model stopped reacting to the sculpt mode brushes and won't move at all. I was able to sculpt the same vertices earlier for the other shape keys and they still move if I change their weights. I tried all of this to try to figure out what's going on:


Isolated the "frozen" vertices by deleting all the other ones.
Deleted all other objects and modifiers in the project.
Deleted all the shape keys
Extruded some of the frozen vertices (by extruding edges) to create new geometry
In edit mode added a UV sphere as part of the same object where the frozen vertices are


The frozen vertices and the newly created by extrusion remained frozen and impossible to alter by any of the sculpt mode brushes. I was able to sculpt the newly created sphere without any issues.

I then applied a modifier to the object with the frozen vertices (tried with subdivision or with bevel) and this un-froze the vertices and I was able again to sculpt them. Is the vertex data corrupted? Is there a way of fixing this in the full project (I can't apply modifiers without loosing all my shape key work)?

Project file with the frozen geometry (can you sculpt this?): Blender file
This vertexes are masked. https://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.64/Sculpting

Masks are used to "protect" parts of the model from being edited by the sculpting tools. They appear as darkened areas of the mesh. The darker a masked area is, the less effect sculpting on it will have. Masks can be edited with the mask brush, as well as cleared or inverted accross the entire model. The masking feature is active as soon as sculpt mode is entered; there is no separate toggle.

To clear mask use Alt+M