mozilla-services
A user's home page is taken instead of a thread on Twitter
When you try to take a full screenshot of a conversation window it takes a page in the background instead.
I can reproduce this issue on Firefox 57.0.3 and latest Nightly 59.0a1 build. When you take a full screenshot on a thread, it seems that only the visible part of it is displayed where it was originally positioned over the Twitter homepage. See this screenshot: https://screenshots.firefox.com/QM5YRNjXuNS5sYfm/twitter.com
If the homepage has a lot of content loaded (>5000px of Firefox, >10000 px on Nightly) and you take a full screenshot on a thread positioned lower on the page, then the thread is not displayed in the shot, because it was cut off. @abbiefl probably that's why only the homepage is displayed in your case.
Can confirm this:
Full screenshot: Tread not shown at all. Manual "dragging" and moving the dragged area out of the visible space: At the edge of the visible space, the thread is cut of and the homepage (i.e. background/timeline) is shown.
Firefox 57
