Autodesk just released a hotfix for Revit 2020.2 and if you haven’t installed it yet, do it ASAP. The 2020.2 release has a bug (discovered recently through customer reporting) where in projects upgraded to 2020.2 some families would disappear or become corrupt. This hotfix is to prevent this problem from happening on projects that have not yet been upgraded.
Click here to read the article on the Autodesk Knowledge Network about the issue.
Here’s info about the hotfix itself. It is important to note that this hotfix will prevent the issue from happening on newly upgraded projects but will not fix corrupted families in projects that have already been upgraded.
You can download the hotfix from manage.autodesk.com or through the Autodesk Desktop App.