unluckily I cannot share any screenshot, but the problem is as follows:

We click in the 'Permissions' button.

Then we add the groups to grant access.

Click on 'Add'.

Click on 'Save' button.

After this, we go again to the permissions section and the groups granted previously are not there. 

Not sure if this has anything to do with the control plane version, but it seems that databricks team is changing a lot of things and we cannot track every new feature changed from the past. Another example could be the naming they follow, you learn something as it is right now and nothing confirms you that it will never change unexpectedly, we should be able to control the version of the control plane to avoid this kind of situations...