Only 2 days of history in Safari (High Sierra)

Since upgrading to High Sierra (currently I am using 10.13.1), my Safari history only covers the current day and the day before. All entries older than two days (or actually maybe older than 24 hours!) are gone. Setting "Remove history items" is (and always has been) set to "Manually" which means "never" to me. I am actively relying on my browser history since I do not maintain bookmarks anymore.

1 - How can I convince Safari to behave according to its setting?

2 - How can I restore my older history items?

Thanks in advance.