We are trying to prepare our system for a schema change including a new required property, but it doesn’t work as expected.
We use this article as a reference:
According to this, we do the following:
- extended all existing documents in the collection with the new property
- extended the schema on Atlas UI with the new property, and hit save
- just when we hit save, we encounter the following error (see image below)
Why do we get this warning/error?
What does it even mean, to be “sync-compatible”, is there any definition for this?
According to this image this shouldn’t be a breaking change:
Any help/hint would be greatly appreciated 
