When some mods are enabled, and when using the R&F ruleset (vanilla game is not affected), some (ie "random") DLC may try to load their R&F compatibility file (like CivilizationName_Expansion1.xml) before the base data for the DLC is loaded, resulting in a DB lock because of missing references and sending the user back to main menu.
My workaround is simply a few edited .modinfo replacing the game's files, to manually set a load order of "2" for the files updating the DLCs for Rise and Fall. (A load order of "1" works too and is used in some other versions of this fix)
The fix can be downloaded here:
https://forums.civfanatics.com/resources/workaround-when-returning-to-main-menu-with-r-f-and-some-mods.26701/