If this is intermittent then it means your wifi is intermittent, it is loading the raw web page (as you say, rather old school) and then failing to load additional parts of the page such as style sheets and scripting.
In this case working on wifi signal is the first step, and the page to start at is:
https://duet3d.dozuki.com/Wiki/WiFi_disconnections_and_AJAX_timeout_errors
This could also be due to ad/spam blockers in a browser, but it would be permanent if so 😉