After investigating: It appears that if a Wikibase instance has some local properties and federatedProperties is enabled, many used local properties will appear as deleted properties if the property Id do not exist on the remote Wikibase. Otherwise, the Remote properties override the local properties and show an error message if the current value does not match the expected data type from the remote Wikibase property.

Details

Initial state: Federation is Off
Federation is off with only two properties existing and one Item.

Next state: Federation is On

• Federation is on and the statements are added to the item using federated properties.
• Here the statement using local properties shows a deleted property error on the statement.

Next State: Federation is Off again

• Once federatedProperties is disabled, the local properties reappear normally on the page.
• The statements made with properties from federation are displayed as deleted properties.
• I created more properties at this stage till P17 ( P17 exist on Wikidata so I wanted to have a p17 locally too )
• I used P17(datatype is string here) to add a statement to Q1 and saved.

Next State: Federation is On again

• the statement using p17 now shows a different label and expects a different datatype which is not what the value saved satisfies. So a datatype error is shown.
• The list of properties shows only properties that were made at the initial state (2 out of 7).

While I was switching FederatedProperties between enabled and disabled, I was a little scared many things will blow up and expected more error. But all seemed to work still fine at least for the pages I visited.

Just to mention: I tried this on 2 Wikibase instances. The first one gave me a lot of errors so I deleted and installed a new one and started all over. and the second was smooth so I am assuming my first try had some installation error that made things explode.

I changed my cache setting from $wgMainCacheType = CACHE_NONE
set in LocalSettings.php $wgMainCacheType = CACHE_ANYTHING and enable Federation.

The list of properties page shows all properties from P1 to P17 but for properties also existing on the remote Wikibase, their label is overridden, though when you click on the property link it takes you to the local property page.

+1 from me for the content of this ticket.
And the followup is already T246128

+1

In T255404#6234274, @Addshore wrote:

And the followup is already T246128

I think it is even the more specific T255651, which is the follow up task. This one here could be added to the description over there, in addition to T255137.