Uncaught (in promise) TypeError: a is not a function

I am trying to create a new page and am receiving the following error on https://www.dkbfoundation.org/wp-content/plugins/gutenberg/build/api-fetch/index.js?ver=1563569117

Uncaught (in promise) TypeError: a is not a function
at index.js?ver=1563569117:1
at t (index.js?ver=1563569117:1)
at index.js?ver=1563569117:1
at _ (index.js?ver=1563569117:1)
at API_FETCH (index.js?ver=1563569117:1)
at index.js?ver=1563569117:1
at index.js?ver=1563569117:1
at Array.some (<anonymous>)
at n (index.js?ver=1563569117:1)
at index.js?ver=1563569117:1

The page I need help with: [log in to see the link]