Tabs lost in FF 55

[muranyia]

I was to migrate/save my tab groups but before that, they have died in my FF 55 (Linux).
Once I change the group I have no tabs any more, and clicking on Tab Groups brings up the screen with the groups but they are empty. (As long as I don't change the group, its tabs are still there on the tab bar but not in the Tab Groups screen.)

Do you know a way to get them back so that I can at least save them?

[grahamperrin]

Maybe some overlap with the Mozilla bug (not an issue with Tab Groups) that affected many users of Firefox 55?

• 1388628 - Tabs are all restored as blank frequently