This is a new feature I don’t even know if i should call this a new feature for team create that allows multiple people to Edit scripts. You can disable it in Game Settings > Options If you want to make use of the future here is what you do.
Go to View and enable the Drafts widget. When you edit scripts it should show up in there. Click on the script and right click then click Commit or you can select the script and click the blue commit button. If someone else commited to the same script a Green icon will show up. Now you can’t commit anymore, instead you can merge your draft or look at the changes.