I would like to suggest a warning or prevention mechanism for field groups when saving if two fields have the same field name.
I recently had a large scale project with many field groups in which a new field was created with the same name as a previously created field in that field group. The addition of a new field with the same name caused us to lose all of the data from the existing field, which was a repeater field that held a lot of data that was time consuming to input
A little warning/notice or flat out preventing the field group from saving (similar to saving a post without filling in a required field) would have been a huge help in our case. Even with just a warning, we could have changed the new field’s name prior to saving the posts and losing data.