Uncaught Error: Syntax error, unrecognized expression: #

When I click on edit paragraph, the following error is shown in the Console:

drupal.js?v=10.3.8:64 Uncaught Error: Syntax error, unrecognized expression: #           
   at I.error (jquery.min.js?v=3.7.1:2:11769)
    at Y (jquery.min.js?v=3.7.1:2:17234)
    at re (jquery.min.js?v=3.7.1:2:20008)
    at Function.I [as find] (jquery.min.js?v=3.7.1:2:7520)
    at ce.fn.init.find (jquery.min.js?v=3.7.1:2:21991)
    at new ce.fn.init (jquery.min.js?v=3.7.1:2:22483)
    at ce (jquery.min.js?v=3.7.1:2:1077)
    at loadAjaxBehavior (ajax.js?v=10.3.8:44:29)
    at Array.forEach (<anonymous>)
    at Object.attach (ajax.js?v=10.3.8:52:40)

Then the CKEditor is not loaded, fieldgroups are not working, etc..