It seems your caching plugin removes version info from CSS and JS files.
The problem can occur when the plugin is updated since the new plugin also provides new javascript and CSS files. In order to prevent browsers from loading old js/css files the plugin appends version info as query parameter to js and css files needed.
However, on some websites this version parameter is removed (very likely due to aggressive caching) and this may cause problems.
https://adinserter.pro/documentation#missing-version-parameter
Because of this the old cached files (css and js) are loaded which cause warnings and unpredictable behavior. If you are using caching make sure the caching software DOES NOT REMOVE VERSION INFO (QUERY STRING) parameter from the urls on the settings page. This is needed for browsers to reload the file when the plugin is updated.
Possible caching utilities that might affect query strings:
– Cloudflare: Caching level / Deselect Ignore Query String as it may remove query strings
– W3 Total Cache: Uncheck Browser cache / Remove query strings from static resources (although it should not cache backend settings page)