Revit 2020.2 Corrupt or Unusable Families Issue

Autodesk posted an article describing a particularly unpleasant bug/issue that started to appear shortly after 2020.2 was made available. This is the text from the article. If you're using 2020.2 pay close attention, you don't want to catch this bug. They've removed the 2020.2 download until they've resolved the situation.

Issue:
The Revit team has identified a defect with Revit 2020.2 that affects a small percentage of customer projects. In order to reduce the likelihood that customers come across this issue, we have temporarily removed the Revit 2020.2 updates while we work to provide a build that remedies this defect. For customers that have already installed Revit 2020.2, please see the FAQ below. We apologize for any inconvenience this issue may have caused.

Solution:

Q. What is the issue?
A. A change in the way that Revit 2020.2 processes families can cause family content to go missing from workshared central models created in previous versions if the families have existed in an active project for a long time without being modified. The defect results in the deletion of the family content from the central model.

Q. Which versions/models are affected?
A. This issue affects only Revit 2020.2. Previous versions are not affected.

Q. What models are affected?
A. The issue can affect workshared models that were created or upgraded in Revit 2020.0 or 2020.1 which are then repeatedly modified in Revit 2020.2. This issue can impact central models stored locally, on Revit Server, or in Revit Cloud Worksharing. The following models are NOT affected:
Non-workshared models
Workshared models created and exclusively modified in Revit 2020.2

Q. What if I have already installed Revit 2020.2?
A. If everyone on the project team is working in 2020.2, there are a few one-time operations you can take in a Revit 2020.2 build to prevent the issue:
Rename all families in the project (e.g. FamilyX to FamilyX-2 and then back to FamilyX)

OR

Save the model as a new central (must be a new file, not Save As to the same location)

OR

Reload all families (including company, Autodesk, and 3rd party families) in the project

OR

Move the entire project team back to Revit 2020.1
If the team is working on mixed versions, we suggest first getting everyone onto the same version. Working in a mix of Revit 2020.2 and earlier versions can reintroduce the issue to model(s).

Q. What is Autodesk doing to resolve the issue?
A. The Revit team has reproduced the issue and is actively working on a build that does not contain this defect. In the meantime, we advise against installing Revit 2020.2 until the Revit team provides an updated build. To reduce the likelihood that customers come across this issue, we have temporarily removed Revit 2020.2 updates from Accounts and the Autodesk Desktop Application. Due to backend constraints a full install of Revit 2020.2 continues to be available from Accounts.

Q. When will a fix be available?
A. Thanks to the support of our valued customers, the Revit team has been able to reproduce the issue and has identified a fix. In the next few days we will be thoroughly testing the fix. Assuming all goes well, it will then take the team a few more days to make the build available in Accounts and the Autodesk Desktop Application.

Q. Revit 2020.2 has been available for months – why didn’t Autodesk communicate anything previously?
A. The Revit team was first made aware of a possible issue by our customers a few weeks ago. Since these kinds of issues can be difficult to reproduce from scratch, from the time a concern was raised we have been working closely with those customers to reproduce the issue. We were finally successfully able to reproduce, and therefore confirm, the issue at the end of last week when we took action to limit the availability of Revit 2020.2. We have been working diligently to clarify the full scope of the impact and the possible workarounds in order to write this communication.

Q. Why didn’t the Revit team discover the issue during pre-release testing?
A. Unfortunately because this issue requires a combination of model creation and modification of families in a previous version and then extensive modification to the same model in 2020.2 it does not lend itself well to typical testing practices or automated regression tests. This means that unfortunately, despite rigorous Revit 2020.2 testing, we were not able to identify the issue before it affected customer models. We sincerely thank the customers that escalated the issue to us so that we are now able to take appropriate action.

Q. What actions will the Revit team take to prevent this kind of issue from happening again?
A. After the Revit team resolves the immediate issue, we will be holding a retrospective to clarify how the defect occurred and what specific actions we can take to prevent similar issues in the future. As much as possible we will look to create automated tests to cover this kind of situation as that means that every future Revit code submission will be scanned for similar problems.