Blender Armature Rotation causes Scaling I'm still new to rigging in Blender, but I'm working on a basic door. I have a door with a doorframe and two doorknobs on either side. 

To rig it, I did the following:


Create a door. The doorframe, door, 2 x doorknob base, and 2 x knob
itself are separate meshes joined together with ctrl+j. Make sure it is scaled to 1 in every direction.
Create vertex groups: 1 includes the door, doorknob base, and knob.
Two other groups include each separate doorknob.
Create an armature. Enter edit mode and scale slightly smaller.
Extrude the root bone and disconnect it. Move the bone into the hinge
of the door so I can open and close it. Name the bone to match a
vertex group containing the door and doorknobs.
Extrude the root bone and disconnect it. Move it into the center of a
doorknob so I can rotate it. Name the bone to match the name of the
knob.


The problem I'm finding is that if I rotate that bone for the doorknob, it also scales the doorknob down and back up. I found an earlier post about it that said maybe there was a problem with the armature, so I deleted my armature and re-did it, making sure to only ever scale, rotate, etc. the bones in edit mode with that bone selected. I'm not sure what else to check to troubleshoot why rotation also causes scaling, since it seems very counter-intuitive. 

Link to blend: https://www.mediafire.com/file/y8vh8fvqh41rzva/upload_door.blend/file
I did not realize that if I opened up the object and looked at the modifier for the armature, I would have the option to preserve volume! It seems that is the setting I was looking for. I have an inkling that what was said in the answers here about the distance between the root and other bones might be the reason. Either way, once applied, my doorknob no longer shrinks.