As discussed on the forum here http://forum.unity3d.com/threads/animation-animator-problems.337987/#post-2221440.

1. While working on an animation (in record mode), save the scene.
2. Record mode should turn off automatically.
3. Make a modification in the scene while record mode is off.
4. That modification will be added to the animation, and a single error message will appear.
5. Turn on record mode, save the scene. Record mode will automatically turn off. Repeat multiple times.
6. When making a modification when record mode is off, you will see 1 error message for each time you saved the scene while in record mode.

This tells me that some event is registered when entering record mode, but when saving the scene to turn off record mode, that event is not unregistered.

Reproducible with 5.4.0b3
Regression from 5.3.2p1