Rudder

To reproduce, create two groups with the same property, but with different values. Make sure to have at least one node in it.
Resolve the conflict by creating a new group from the intersection of the previous two.
Then try to acces the property webpage of the latest, you can't.

There is no good reason to make it unavailable as the following could be a pretty common scenario:
Let's have 3 groups: AWS, Production and 'Production in AWS'.

1. Let's define a 'exception' property in the 'Production in AWS'
2. Now let's define a 'test' property in the AWS one
3. And creating the same one, with a different value in the Production group

The 'Production in AWS' should now resolve the conflicting 'test' property but still define the 'exception' one. Currently, it makes the 'exception' one impossible to edit.
Also, this is a common case when trying to resolve a complex case of property overriding. And not being able to visualize the conflicting properties in the resolution group is a major pain.