Operating system: Windows 10
Graphics card: NVIDIA GeForce GTX 1060 6GB
Short description of error
If object has keyframe animation and a new object is created by separating geometry, then any edits made to the keyframe animation of one is applied to both the original object and the new one.
Exact steps for others to reproduce the error
-Add a minimum of one keyframe to the transformation data for the default cube
-Go into Edit Mode
-Select some of the geometry and separate it into a new object (P)
-Return to Object Mode, and with the new object selected, try deleting the keyframe, adding a new one, replacing the one there with a different one, etc, and once you refresh the frame, any of those changes will have been applied to the original object as well. The same will apply vice versa (any changes made to the original object's keyframe animation will also apply to the new object).