This is a great add-on but v0.16.6 has bugs.
#1. Click on icon > dropdown menu with groups opened > select an item > nothing happens! (now if you click on icon again an empty menu opened. additionally F2 not working and the settings page has broken items).
#2. Restart Firefox and press F2 > page with groups opened successfully > click on a Tab from another saved Tab group > Firefox switched to this group normally (now again icon menu, F2 and settings page broken like #1 above).
#3. I had no problems at all using versions before 0.16.6.
#4. FYI i am also using "Temporary containers v0.91" add-on (installed months before this add-on).


EDIT: Yes it is fixed in 0.16.7 - Thanks for quick responce - B. Regards