Probably because you have double geometry!
Meaning, two of the same mesh data in the same object.
Because of mesh extrusion (e-key) which was canceled in action.
- select all mesh in edit mode: press
a
- then merge by distance
But if you already have applied the bevel.
- select the unbeveled vertex and press lowercase
L
for linked selection - delete the selection, this will throw away the duplication
If you press e
to extrude, the extrusion already took place and Blender is automatically waiting for the user to move the extruded part. If you don’t do that or cancel the action (ESC), then you have vertex duplication and problems ahead.
Meaning duplication, which you don’t see immediately. But giving you problems like this.
best approach is to do regularly a merge by distance, when working with the extrude e
option.
Ok… doesent seem to work… I guess start from scratch ans watch out for the e
Then check for double objects!
Check if you have two pillar objects on the same spot!
- select an object and press
h
for hide, etc … - To unhide all, press
alt-h
- follow/check the icon behavior in the outliner panel (top right) the
Delete one pillar.
As it is a keyhole view, we can not see but perhaps you have a mirror modifier on this and it is set to operate in more than one axis?