Classic Editor has become unuseable

[gareth3lee]

I volunteer to run a WordPress website hosted via cPanel for a not-for-profit organisation. They have a legacy site with a custom theme which is about 10 years old. They receive updates for Worpress and other components via cPanel, but not their theme since this was customised at the time of creation. Prior to a month ago all was working well.

About 3-4 weeks ago their editor ceased to work and displays a chaotic and disfunctional layout when I login: looks like a possible CSS problem to me (see attached screenshot after login as admin). The site itself still operates and serves pages correctly.

After a little detective work: They are running WP 7.0 on PHP 7.4.33. (I tried updating PHP but this crashed the site entirely so I had to revert.) I also notice an update of Classic Editor from v1.6.7 to 1.7.0 over the past month so this might be a cause. (Not obvious in cPanel how to revert to older version.)

Can anyone suggest how I might get the editor running again as my knowledge of WP is very limited beyond editing content via .../wp-admin? I would greatly appreciate some suggestions from more experienced users how to get this back on track. (I'm fairly capable with cPanel and the linux command line if you wish me to conduct more tests etc.) Thanks!

[gareth3lee]

This is the dashboard display after logging in as admin.

[audrasjb]

Hello this looks more like something that should be addressed in a support forum topic, rather than a WordPress Core bug as it involves a custom theme, the classic editor plugin, and maybe other plugins.

Therefore, I'm closing it as invalid, which doesn't mean that the request for help is invalid, but that it should be addressed on support forums: ​https://wordpress.org/support/forum/how-to-and-troubleshooting/