In this thread, zero gave us an update:
I’ve given the go-ahead to re-enable the Foundry editor!
For projects that were seeing problems with “sunken” objects, before you start fixing things, make sure to preview your map. Most/all of these problems were already corrected and just require republishing.
We didn’t want to remove all the Foundry missions again and make them all go through another republish.
It may take a short while for the editor to come back up.