Currently, the inverse kinematics dragger in Studio will mysteriously rotate MeshParts and Unions if moved with the Move Tool handles, even if they have no constraints. This should probably not happen.
The setting to enable IK dragging is a very small button in the top bar that is easy to enable accidentally, or forget to disable. Developers with this setting enabled are confused when this happens and have reported this as a bug in the past. There have been a couple of threads regarding this issue, and dozens of posts about this in both the new member and member Discord servers.
Since this only seems to occur for MeshParts and Unions, this seems like unintentional behavior and should probably be changed. Parts should not be mysteriously rotating.
I was told this might be a feature request but it feels like a bug report to me.