“Todays hotfix follows in the footsteps of Update 39284 with a handful of important fixes for issues that cropped up in last weeks build. This includes the notable pauses during gameplay, AI behaviors that proved disruptive to players, the loss of the final chapter in the Saladin campaign, a misrepresentation of ELO changes following ranked matches, and more.”
Source: N4G PC Age of Empires II: Definitive Edition Hotfix 39515