Summary: Whenever Chromium tells you "restart to apply updates", make a backup in TabFern, then restart right away!
This is caused by upstream https://bugs.launchpad.net/snapd/+bug/1616650 . When the Chromium snap refreshes, and you get a "restart to apply updates" notification, saving of data is silently disabled until you restart Chromium. There is not much that TabFern can do about this, unfortunately.
Summary: Whenever Chromium tells you "restart to apply updates", make a backup in TabFern, then restart right away!
This is caused by upstream https://bugs.launchpad.net/snapd/+bug/1616650 . When the Chromium snap refreshes, and you get a "restart to apply updates" notification, saving of data is silently disabled until you restart Chromium. There is not much that TabFern can do about this, unfortunately.
214 would help with the workaround.