Blank Page Editing Posts/Pages

Hi,
in our wordpress network, it is no longer possible to edit pages or posts in the backend (on any site).

By clicking on the edit of any content, the result is always a blank page.

In one of the sites I “unlocked” the situation by activating the “Classic Editor” plugin, but clearly, I didn’t want to make it available.

There aren’t errors in the server logs.
By activating the WordPress option WP_DEBUG to true, there are no reports from the system.

Via the browser’s DevTools I only encountered these error messages:

(1) An error occurred while running ‘mapSelect’: n (…) is null data.min.js: 2: 20528

(2) TypeError: Object (…) (…) is undefined
Stack trace:
Xs @ http: //blog.unimc.it/wp-includes/js/dist/edit-post.min.js? Ver = 3656613c515e40e95a15114467097b39: 49: 131322
we @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? ver = 16.13.1: 84: 293
zj @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? ver = 16.13.1: 226: 496
Th @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? Ver = 16.13.1: 152: 223
tj @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? ver = 16.13.1: 152: 152
Te @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? Ver = 16.13.1: 146: 151
Ja @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? Ver = 16.13.1: 224: 381
md @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? ver = 16.13.1: 173: 43
nd / <@http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? ver = 16.13.1: 175: 222
Rh @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? Ver = 16.13.1: 147: 64
nd @ http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? ver = 16.13.1: 175: 208
I.render@http: //blog.unimc.it/wp-includes/js/dist/vendor/react-dom.min.js? Ver = 16.13.1: 238: 412
el @ http: //blog.unimc.it/wp-includes/js/dist/edit-post.min.js? ver = 3656613c515e40e95a15114467097b39: 49: 135127
window._wpLoadBlockEditor </ <@http: //blog.unimc.it/wp-admin/post.php? post = 330 & action = edit: 2037: 13

Server configuration:

• WordPress Version 5.8.1
• Linux 4.7.0-0.bpo.1-amd64 # 1 SMP Debian 4.7.8-1 ~ bpo8 + 1 (2016-10-19) x86_64 GNU / Linux
• PHP 5.6.30-0 + deb8u1 (cli) (built: Feb 8 2017 08:50:21)
• Server version: Apache / 2.4.10 (Debian)

• This topic was modified 3 years, 5 months ago by James Huff. Reason: moved to Networking WordPress since this is a multisite question