I looked at the website again and noticed that the request paths looked odd, one of them being `/400_random_url_with_numbers_403`. I googled that and it looks like it's part of a client-side bot detection script that's testing something, the explanation isn't very informative.

https://my.f5.com/manage/s/article/K000138794

> These requests are caused by the bot profile to test the different browser capabilities.

> 'http://127.0.0.1:xxxx' request is a call to the localhost/client machine, which is normal when trying to protect assets like end-server using ant-bot defense. It does not have any impact regarding application page load.