If you repeatedly open and save the attached glade file, rather than staying the same, it will cycle between two states, each with a large chunk of changes between the states (diff also attached).

This is obviously extremely annoying when storing files in revision control. I don't mind (too much) if the output changes between versions of glade, as long as it's not too often, since I can just commit an otherwise no-op change with just those differences and ask all contributors to upgrade in sync, but it's a major problem for me when every change made in the UI will produce a significant diff.