iPadOS 13 Beta 4 and 5 destroyed a safari window with many open tabs

I had a Safari window in iOS 12 and early versions of iOS 13 which had hundreds of tabs, both in regular and private mode and when I select that window from the task list (it says that Safari window has > 400 tabs open) it comes up with only one tab in regular and private mode.

I have Safari -> Close Tabs set to Manually.

I have done many restores from earlier backups and afterwards, every time I go to that window from the task list it loses all its tabs. Is this a bug or a feature? Has anyone else had this happen?

Thanks.