Just noticed that if you put your mouse cursor on the thread list in a place where the scrollbar normally displays you won't be able to scroll because there will another top-level scrollbar (for some reason on production I can only reproduce it in cases where the threads don't fill the whole list).

This was introduced when I landed ENG-3976 because the thread list container now contains the react-window list and the scrollbars overlap each other. This is a quick fix that sets overflow: hidden on the container (we don't want to scroll it, the scrolling is handled by the inner list).

Try the reproduction mentioned in the summary and check if the scrolling works and the second scrollbar doesn't appear