The Revit 2020.2.9 Hotfix was released to address specific issues reported by users after the initial 2020.2 release. It is a cumulative update in some contexts, but typically these "point" releases focus on stability and specific bugs (such as file stability or interactions with BIM 360/Cloud models).
The 2020.2.9 update specifically targets several performance and stability issues: revit 202029 hotfix updated
Users reported that in rare cases, saving to the cloud (BIM 360 Document Management) would produce error "Model Cannot be Saved – 202029". This hotfix specifically targets and eliminates that error. The Revit 2020