Hello! 
When I try to change the order in one category in Project Manager (Scenes, External Events, External Layouts) using the search tool and have at least one that the search tool don’t get it the bug happens. In my example I did the external layout “Old” to search tool don’t get it and filtred for “New” trying to change the order:
As you can see it doesn’t respect the order I changed. It had strange behavior. Thanks!