It has recently come to my attention that ArcGIS Pro will allow you to name a map the same thing as another map already within your project. This is generally avoided, if you import a layout, it adds a "1" at the end, but if you miss a step, or accidentally rename a map, it will not give you an error, but will ALLOW you to name maps with duplicate names.
This should be fixed ASAP as it causes huge errors, especially within pro projects with multiple maps and layouts.

