Broken: 2.79b f4dc9f
Short description of error
I locked 2 groups, I clicked "Delete all unlocked groups" in the menu.
However, all groups are cleared, both locked and unlocked.
I found that its not working only after working a while on Blender, like assigning and removing vertices from groups, switch edit mode on/off etc.
If it's not working, the following steps can make it work again for a while, for unknown reasons...
- new a startup file
- open the .blend file you saved in step 1