@Marcos F5 doesn't work.
@itman I've tried it in a fresh Windows 10 VM on these different browsers:
Firefox 77.0.1
Chrome 83.0.4103.116
Edge 83.0.478.56
In all tests, before installing ESET Smart Security, the sites were presenting no problems, after installing (and waiting for Web Access Control to finish loading), the JavaScript files started coming scrambled accross all browsers, and after uninstalling ESET, it all went back to normal.
Another symptom in https://www.oxfordlearnersdictionaries.com, besides the lack of dictionary change option, is that the search bar doesn't really work when this issue occurs.