When selecting and attempting to export all or many objects from the User interface (UI) under Admin > Import/Export, the export process never completes to where you can select the export button to download the XML file. It works fine when only selecting a few objects. There are no export related errors in the aveksaServer.log, but the UI does appear to timeout.
Your system is likely busy and the metadata export process is taking longer than allowed for the session timeout limit.
Increase the User Session Timeout limit in the UI under Admin > User Interface > Settings. There is no need to restart the application. If there are concerns about the longer session timeout period, you can do it temporarily and reset it afterward or you can download a smaller quantity of objects either by object type or by selecting individual objects.