While examining web server logs @ MDL-73019 (part of the PHP 8.1 Epic), this problem has been detected. It happens 14 times in logs (note the logs in that issue are aggregated from 3 different behat jobs, so they could be 2-6-6 or any other combination).

218803:[Sun Feb 12 12:10:17.109398 2023] [php:notice] [pid 5252] [client 172.29.0.4:41404] Debugging: Invalid get_string() identifier: 'nowarningsonselected' or component 'tiny_accessibilitychecker'. Perhaps you are missing $string['nowarningsonselected'] = ''; in /var/www/html/lib/editor/tiny/plugins/accessibilitychecker/lang/en/tiny_accessibilitychecker.php? in

• line 356 of /lib/classes/string_manager_standard.php: call to debugging()
• line 109 of /lib/external/externallib.php: call to core_string_manager_standard->get_string()
• line ? of unknownfile: call to core_external::get_string()
• line 251 of /lib/external/classes/external_api.php: call to call_user_func_array()
• line 83 of /lib/ajax/service.php: call to core_external
  external_api::call_external_function()
• line 33 of /lib/ajax/service-nologin.php: call to require_once()
  , referer: http://webserverd658860a71ecf312/behatrun1/user/editadvanced.php?id=2&course=1&returnto=profile

So this issue is about to fix that missing lang string (or lang file) and ensure that it doesn't appear on weblogs anymore (non-js and js, both boost and classic).

Ciao

PS: This only has been checked in master (4.2dev), so it may happen in older branches too, although the problem was not detected in 4.1.0 release testing @ MDL-76064