When you edit or move an address for a person who has more than one address using the placeholder postcode like ‘XXX XXX’ Mosaic skips the usual check that excludes unknown addresses from multiple address moves. Instead, it pulls in all records with that same unknown address and doesn’t let you choose which people to move along with it. If there are a lot of people linked to that address, it can also cause the system to freeze.
From version 22.0.0.0, Mosaic will now use report filter 'Unknown Address' to identify the post code for unknown addresses.
Mosaic will exclude unknown addresses (mapped to the 'Unknown Address' report filter) where a record has the unknown address recorded more than once.