Since new API sometimes we returns ZoneDateTime instead of Date in a JSON map result.
On client side instead of a readable date such as yyyy-MM-ddThh:mm:ss we receive :

"creationDate":{"offset":{"totalSeconds":0,"id":"Z","rules":{"transitions":[],"transitionRules":[],"fixedOffset":true}}

As consequence, in list of workspaces in admin for example the creation date is empty.
There may be other issues like this...