Thank you very much for the video!
I tried in different browsers and deactivated other plugins but it still wont work. I found this error code in the console:
load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils&ver=5.3:8 JQMIGRATE: Migrate is installed, version 1.4.1
jquery.mCustomScrollbar.min.js?ver=2.0:1 A parser-blocking, cross site (i.e. different eTLD+1) script, https://cdnjs.cloudflare.com/ajax/libs/jquery-mousewheel/3.0.6/jquery.mousewheel.min.js, is invoked via document.write. The network request for this script MAY be blocked by the browser in this or a future page load due to poor network connectivity. If blocked in this page load, it will be confirmed in a subsequent console message. See https://www.chromestatus.com/feature/5718547946799104 for more details.
(anonymous) @ jquery.mCustomScrollbar.min.js?ver=2.0:1
(anonymous) @ jquery.mCustomScrollbar.min.js?ver=2.0:1
jquery.mCustomScrollbar.min.js?ver=2.0:1 A parser-blocking, cross site (i.e. different eTLD+1) script, https://cdnjs.cloudflare.com/ajax/libs/jquery-mousewheel/3.0.6/jquery.mousewheel.min.js, is invoked via document.write. The network request for this script MAY be blocked by the browser in this or a future page load due to poor network connectivity. If blocked in this page load, it will be confirmed in a subsequent console message. See https://www.chromestatus.com/feature/5718547946799104 for more details.
(anonymous) @ jquery.mCustomScrollbar.min.js?ver=2.0:1
(anonymous) @ jquery.mCustomScrollbar.min.js?ver=2.0:1
prBackendVariablesDeclarationFooter.js?ver=5.3:696 Uncaught TypeError: Cannot read property 'insertHtml' of undefined
at HTMLSelectElement.<anonymous> (prBackendVariablesDeclarationFooter.js?ver=5.3:696)
at HTMLSelectElement.dispatch (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils&ver=5.3:3)
at HTMLSelectElement.r.handle (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils&ver=5.3:3)
(anonymous) @ prBackendVariablesDeclarationFooter.js?ver=5.3:696
dispatch @ load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils&ver=5.3:3
r.handle @ load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,utils&ver=5.3:3