Board Thread:Support Requests - Getting Technical/@comment-30861564-20170112012009/@comment-197.218.91.198-20170113212242

Err, javascript can alter the behaviour of any page, and different scripts can interact in unexpected ways. It is one of the reasons why it is deactivated in certain special pages for security purposes.

To put it simply, it is caused by some faulty Javascript programming logic, is also the cause of many so called non-existent bugs regularly reported here. Wikia staff really should add that to their bug report form that people should really disable all javascript / gadgets & CSS and retest before reporting anything (even on forums).

In fact, it is an advice  in one of a comments in a staff blog post about reporting bugs.