Vertex jumping when moving objects with the mirror modifier I was working on a character using mirror mode. I then created a separate object and joined it to the main mesh. However, after I tried moving this object, a few vertices from the end of the mesh would jump to the mirrored portion of the character:


I tried replicating this effect in other files, but it didn't always happen.

Is this a bug? Is anyone else experiencing it?

Note: This was in blender 2.77, with on additional plugins installed. The mesh had a subsurf modifier on as well, but the jumping occured even if I removed it.
It happens to me time to time as well, but only when I forget to uncheck 'x mirror'in the Tool Panel within the Options Tab. 

If that is checked and you only have half a mesh in the case with a mirror modifier, Blender will try to calculate the missing halves verts by pulling them over to the missing side.

Either way, just uncheck it and things will be back to normal. :)