Recently, I have been having an issue where adding a word to one of my languages' dictionary causes the web page to stop responding and my browser to slow significantly until the tab is closed. The word is added - I can confirm this by searching for it on the language's user-facing page - but I have to close the browser tab and re-enter the old version editor for the article if I want to add more. Just after adding the word, right after the browser tab starts hanging, the list of words in the left column of the dictionary tabs disappears from view.

It happens when I try to edit this article. The number of entries may be a factor, but I've only had performance issues on low-end machines before.   1. Go to the dictionary tab in the old version editor on a language article 2. Fill out the information boxes for a new word 3. Click "Add to Dictionary" 3a. The browser tab will hang 3b. If the tab is returned to from somewhere else (e.g. checking that the word was entered on the reader-facing page) then the dictionary list in the editor will not be visible when it is returned to