How to fix a critical error in the Custom Routes plugin?

Question

WordPress

The site was configured to automatically add articles (articles were generated by some kind of script and sent via API, most likely to the site), recently articles were no longer added on the Custom Routes page, which, apparently, was made to add an API for adding articles (I can wrong), the following error was displayed (Fig. 1). And so on all pages, no logs could be found. Maybe I was looking in the wrong place, but debug.log was not even generated.

define('WP_DEBUG', true); // не помогает получить код ошибки, к сожалению.

The full list of plugins is below, since I may have mixed up in general and am looking for the problem elsewhere.

1. Advanced Custom Routes - Custom Endpoints for WP REST API
2. Change wp-admin login
3. Clearfy Pro
4. Insert Headers and Footers
5. JSON Basic Authentication
6. Redirection
7. Simple Local Avatars
8. WordPress REST API Authentication
9. WP Realtime Sitemap
10. WP REST API Controller

I can't find the script that added the articles on the server, perhaps it was compiled into a binary or even located on another server, since Custom Routes was added for some reason.

Also, some of the plugins require updating, like WordPress itself, but since I have minimal experience with it, I would like to update last.

In general, what can be done and where to dig?