Twitter embeds breaking block editor

When trying to edit an existing post containing a twitter embed (embedded either via the twitter block or by pasting a tweet URL directly into the editor) you just get a blank white page with the following errors in the console:

TypeError: wp.apiFetch is undefined
Unhandled promise rejection
Object { code: “invalid_json”, message: “The response is not a valid JSON response.” }

If you then remove the twitter embed block (via the classic editor) and save the block editor then works as normal

Re-add a twitter embed and it breaks again

This on WP version 5.2.1 with all other plugins disabled