Cannot edit pages using Admin – page loads but console shows a 500 server error

I'm having a weird issue that cropped up today after updating Grav and plugins. I can log in and use the Admin interface just fine. But when I click on a page to edit it, I'm presented with a page without CSS, JS, etc being loaded, just raw HTML elements.

Checking the browser console shows a generic 500 error when you refresh. Fixing permissions deosn't solve the issue, all the actual pages load fine when viewed on the actual site, this issue is only when editing pages. I tried swapping the theme to the default one and the issue still persists.

Spoke to my webhost in case it was a mod_security issue but they say it's an internal issue with the site. Any ideas what it could be?

@pmurraydesign, I'm afraid I cannot reproduce the issue on a fresh install of the latest Grav + Admin.

You might give $ bin/grav cache or a Clear cache from the Admin dashboard a try