Lots of jQuery Issues

Hi, I have a fresh local install of WordPress 5.5.3, the Gutenberg Plugin and Q (that’s all I have running on the site). I’m having some issues getting the full site editor UI to load in.

There are a number of jQuery errors popping up in the console:

Uncaught (in promise)
{…}
?
code: “invalid_json”
?
message: “The response is not a valid JSON response.”
?
<prototype>: Object { … }

Uncaught (in promise)
Object { code: “invalid_json”, message: “The response is not a valid JSON response.” }

Uncaught (in promise)
Object { code: “invalid_json”, message: “The response is not a valid JSON response.” }

Uncaught (in promise)
Response { type: “basic”, url: “https://www.fse.dev.cc/wp-json/wp/v2/templates?status%5B0%5D…tus%5B2%5D=auto-draft&per_page=100&context=edit&_locale=user&#8221;, redirected: false, status: 404, ok: false, statusText: “Not Found”, headers: Headers, body: ReadableStream, bodyUsed: false }

Uncaught (in promise)
Response { type: “basic”, url: “https://www.fse.dev.cc/wp-json/wp/v2/template-parts?status%5…tus%5B1%5D=auto-draft&per_page=100&context=edit&_locale=user&#8221;, redirected: false, status: 404, ok: false, statusText: “Not Found”, headers: Headers, body: ReadableStream, bodyUsed: false }

Uncaught (in promise)
Object { code: “invalid_json”, message: “The response is not a valid JSON response.” }

Uncaught (in promise)
Object { code: “invalid_json”, message: “The response is not a valid JSON response.” }

Uncaught (in promise)
Object { code: “invalid_json”, message: “The response is not a valid JSON response.” }

I tried installing the Enable jQuery Migrate plugin to see if that worked, but no luck.

Do you have any suggestions for fixing this? Maybe waiting until WP 5.6 comes out?