Why did my Safari tab groups disappear and can I recover them?

I had 9 tab groups open, together about a thousand tabs. After searching something on safari I wanted to read some articles, but opening the tab group screen I saw that only one tab group was there. And that one tab group didn’t have a name. That tab group already existed, but now it had its name deleted.

I want to know if there is any way to recover them and why would this happen?

I have already checked recently closed tabs, but there are only tabs that I have closed before tab groups disappeared. And there isn’t anything at bookmarks.

Thanks for the help

[Re-Titled by Moderator]