Three related issues are causing me some grief:
All of these issues are best seen by selecting, say, the HuffPost Home page and then creating tabs for a large number of stories, followed by stepping through each one and deleting them.
1. Somehow my mouse jitters, producing multiple instances. That's not a bug. When using vertical tabs, the available context menu item to delete duplicates will delete possibly one duplicate. Switching to horizontal tabs, and clicking the much more convenient upside-down caret menu to get the delete-duplicates option kills off many more -- 11 in my last attempt.
2. Having had to revert to horizontal tabs to delete duplicates, when returning to vertical tabs, all my previous settings have been forgotten. In particular, Expand on Hover. This is not a bug, but presumably a choice -- or the absence of one.
3. The actual bug: After some amount of time, although Expand on Hover is still checked, it stops functioning. That is, the bar remains collapsed to left or right margin until the setting is unchecked and rechecked. I reported this before, but the Firefox engineer couldn't duplicate it but it appeared to get better. It still happens though. The best way I've found to trigger the behavior is to spend a lot of time scrolling around in one story, including the "jump to top" action and manual scrolling. After doing this to a couple stories, the behavior pretty reliably appears for me. I'm using the latest overnight releases, as far as I know.
