Hi Hien Phan,
I am facing the same problem when using Sydney or Virtue themes with Learnpress plugin. The lesson keeps loading when user clicks on it. Below is the error text.
main.min.js?ver=20170329:1 Uncaught TypeError: Cannot read property ‘top’ of undefined
at p (main.min.js?ver=20170329:1)
at HTMLDocument.<anonymous> (main.min.js?ver=20170329:1)
at i (jquery.js?ver=1.12.4:2)
at Object.fireWith [as resolveWith] (jquery.js?ver=1.12.4:2)
at Function.ready (jquery.js?ver=1.12.4:2)
at HTMLDocument.K (jquery.js?ver=1.12.4:2)
