System Information
OS: MacOS 10.12.6
Graphics card: NVidia GeForce GTX 775M, 2018MB

Blender Version
Broken: blender-2.79.0-git20170818.ac28a4fba7-x86_64, nightly build of august 18, 2017
Worked: 2.78c, it is broken in 2.79-RC1 and several daily builds after that. Unknown if it works in the inbetween versions.

Short description of error
Undo does not work in Object, Sculpt and Weight paint mode. It does work in Edit, Vertex paint and Texture mode

Exact steps for others to reproduce the error
To reproduce: enter one of the broken modes using the default cube in the default scene, change something, try to undo the action. Undo does not work.

An example: create a new scene, select the default cube. Go into Edit mode, drag out a vertex, Undo the action (CMD-Z on MacOS). This works. drag out the vertex again, go back to Object mode. Undo does not work. Go back to Edit mode. Undo works again and undoes the dragging of the vertex.

--UPDATE AUG-19--
When I first installed 2.79, I copied the settings from the previous version (2.78.5, I think). When I removed the settings directory (~/Library/Application Support/Blender/2.79), Undo worked again in all modes