Check for Updates menu item can cause update failure
Our Torbutton menu shortcut to "Check for Updates" can cause updates to fail if you click on it after an incremental update has already been successfully downloaded and applied, but you did not restart the browser yet. For some reason, it tries to download the update again (the full update mar this time) and then it reports an integrity error.
Clicking on it one more time then restarts the whole update process from the incremental.