Universally in transformers, readers and writers that have the ability for the user to select a coordinate reference system, the pick list presented to the user can really easily be broken and can force an error. For old-FME-timers like me that's just a well trodden peril. But for new users, just starting out it's awkward to tell them that this is just the way things are.
So, in the Reprojector if a user searches for 4326 and finds "EPSG:4326" but doesn't have the foresight to pick it from the list of presented CRS', and instead just clicks the focus away (which is really easy to do)... the user ends up with this getting filled into the dialog "4326". When the process runs that CRS is found not to exist and the process errors at worst and does nothing at best.
Please can this CRS pick list become an uneditable and fixed picklist that allows you to select something from the list or nothing at all. A very simple change but will remove a lot of very frustrating and difficult to debug workspace failures.