NextCloud menu display incorrectly
A strange error happens in some browsers, NextCloud menu become a big page vertically, and one password textbox there requesting password, but the password is not working.
Not specific OS or browser
In my iMac, Safari is not working. In my one Windows machine, Firefox is not working. By the way, the Firefox has sync enabled and it is working in another PC. Google Chrome and Microsoft Edge have no issue.
Debugging
There is programming error, the contents were downloaded from following website directly, not the NextCloud server. Browser blocked them.
https://raw.githubusercontent.com
Solution
Disable "Theming App" in NextCloud Apps screen.