Firestore console shows "Reserved fields can only be edited through the gcloud CLI"

[alexandre-b]

Since a few weeks, I am not able to edit some document fields in the Google Cloud Firestore console (https://console.cloud.google.com/firestore/databases). When I try to click on the pencil icon at the right of field, I see the message "Reserved fields can only be edited through the gcloud CLI" and the click on the button doesn't work.

It only happens on some collections (where all fields are "reserved") but I can still update everything on other collections. Update of documents with the JavaScript SDK works and it's weird but it also works when I use the Firebase console (https://console.firebase.google.com/project/xxxx/firestore/databases).

It seems to be more a feature than a bug as the Google Cloud console UI is consistent (error message, lighter grey icon, button disabled...) but there is no documentation at all about this behavior, what could be a "reserved field" and how to remove this "reservation".

Does anyone have a clue about that?