The showcase currently has a rather low rate limit applied to it. Recently a new showcase design launched (Which included a rewrite of the backend), this should have brought with it a performance boost over the old areas of the showcase which caused performance issues.
The new showcase is reliant upon newer WordPress features, such as the Site Editor which is reliant upon the rest-api, currently these trigger 429 responses pretty quickly due to exceeding the rate limits.
Can we either significantly increase, or remove the rate limits on the showcase please? I would personally suggest removal of the rate limit unless the new design proves to cause issues as previously experienced.