Trying to remove many relationships in the URL editor takes quite a long time.

In this case it took more than 10 seconds. As soon as the page finished loading after submitting them, a "504 Gateway Timeout" was returned. Nonetheless the edits were successfully entered and reloading the page showed the usual "Thank you, your 40 edits (#68237733, #68237734, #68237735, ...) have been automatically accepted and applied."