I spent an hour trying to trace a bug today. (Not helped by lack of debugger.)
Of course it was a very bizarre "bug"
It turns out that Deactivating a group "MyGroup" will deactivate all groups of the same name in all event sheets, not just the Event Sheet that does the activation/deactivation.
It really highlights the fact that C2 needs to have some code analytics.
1. Groups with same name
2. unused objects
3. unused variable names