Operating system:Macos 10.13.6
Graphics card: Intel HD Graphics 3000 512 MB
Exact steps for others to reproduce the error
Intermittent, edit for some time, seems to help if undo commands are issues in quick succession. The message emitted to the terminal is "Skipping auto-save, modal operator running, retrying in ten seconds..."
/Users/awiebe/Downloads/blender-2.79.0-git20190108.e6acb4fba094-x86_64/blender.app/Contents/MacOS/blender --debug Switching to fully guarded memory allocator. Blender 2.79 (sub 6) Build: 2019-01-08 01:48:10 Darwin Release argv = /Users/awiebe/Downloads/blender-2.79.0-git20190108.e6acb4fba094-x86_64/blender.app/Contents/MacOS/blender argv = --debug read file /Users/awiebe/Library/Application Support/Blender/2.79/config/userpref.blend Version 279 sub 6 date 2019-01-04 11:41 hash e6acb4fba094 Read prefs: /Users/awiebe/Library/Application Support/Blender/2.79/config/userpref.blend read file Version 272 sub 2 date unknown hash unknown ordered OBCube OBLamp OBCamera found bundled python: /Users/awiebe/Downloads/blender-2.79.0-git20190108.e6acb4fba094-x86_64/blender.app/Contents/Resources/2.79/python read file Version 262 sub 3 date unknown hash read file Version 268 sub 5 date unknown hash ordered OBCube OBLamp OBCamera ordered OBCube OBLamp OBCamera ordered OBCube OBLamp OBCamera Skipping auto-save, modal operator running, retrying in ten seconds...