Hope it is okay to add my notes here as this seems to be the same issue?   Having the same problem on Spaceport. I'd been editing the world homepage and the CSS. When I added the new custom CSS, looks good, says saved, but then when I reload the CSS is still there but the page does not reflect the new look. So I go into edit and I'm seeing this:
An error occurred while loading Article Page. Please try again later. TypeError   Cannot read properties of undefined (reading 'map')   Copy the message below and send it to the support team.   TypeError: Cannot read properties of undefined (reading 'map') at Object.render (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/index-DqBsBvq0:943:31491) at hu (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/index-DqBsBvq0:298:41953) at Ro (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/vendor-react-euclid-DcqpCCjJ:6:16918) at eu (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/vendor-react-euclid-DcqpCCjJ:8:43908) at Ul (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/vendor-react-euclid-DcqpCCjJ:8:39639) at Vl (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/vendor-react-euclid-DcqpCCjJ:8:39567) at Bl (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/vendor-react-euclid-DcqpCCjJ:8:39421) at Ol (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/vendor-react-euclid-DcqpCCjJ:8:35796) at Ml (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/vendor-react-euclid-DcqpCCjJ:8:36599) at ua (https://wa-js-cdn.nyc3.cdn.digitaloceanspaces.com/assets/prodromos/alchemist/assets/vendor-react-euclid-DcqpCCjJ:6:3271)
  I've tried to attempt a fix, close, and refresh. Note that while I'm clicking to edit the homepage, it seems to be trying to edit an article.   I have also tried closing that article, then going back to editing the homepage. There seems to be a pattern: -view world -click edit gear in top right -editor loads -advanced edit settings pop over editor -edit for other article pops over that -error occurs