Safari History disappearing without manual delete and settings still set to retain for 1 year

My 2024 MacBook Air is running on macOS Sequoia 15.4.1. It is set to retain my Safari History for 1 year, as I use it regularly. Yesterday when I went to use it everything was gone prior to Thursday, 22nd May. I know I didn't manually delete my history, and I went into my settings to check it was still set to a 1-year retention, which it was. After spending some time trying to solve the issue, I reinstalled my History.TP file from my last Time Machine backup, as was advised in another related article on this site, and hey presto, all my history from my last backup backwards was present (although the subsequent few days, including Thursday, May 22nd, and Friday, May 23rd, were not there).

However, this morning I've gone back into History and once again I only have my History from Thursday, 22nd May, until now. I've again checked my Safari settings on my MacBook, and it's definitely set to a 1-year retention. I also checked my iPhone 13, which is linked, but that doesn't have the ability to change the Safari history retention.

So what could be the reason(s) for me losing my Safari History prior to Thursday, 22nd May? How can I stop and prevent this from reoccurring, and other than backing up from my Time Machine, is there another way without installing 3rd party apps to get my History back?