Issue with Multiresolution sculpt: parts of the object cannot be sculpted Parts of the object I am sculpting have stopped responding to the brushes.

A chunk of the object, divided by a harsh line, is no longer capable of being edited in sculpt mode by any means I can find. When looked at from particular angles, the un-sculptable section disappears as well. The dividing line seems to be based on the geometry of the low-res base mesh that was sub-divided by the multiresolution modifier.

I noticed the issue first on the legs of the model, which were not attached, but were part of the same object. I deleted them in the hopes of just creating another object for them later. The issue then appeared on the head after I undid a grab which moved a lot of the face.

Reverting to a recent save sometimes allows the whole face to be edited, but as soon as something is undone, the chunk goes back to being unresponsive.

Changing the sculpt settings (threaded sculpt ect.) had no effect. Changing in and out of object, edit and sculpt mode had no effect.

Thank you for your time.
you should check 2 things:

Is there any &quot;mask&quot; applied (ALT + M to remove any mask applied)
you can sculpt only the selected mesh: if the lower part of the head is another mesh, you need to select it in object mode or join all the meshes so they are 1 single object