Where are manual backup copies kept?

[Running LO 6.1.4.2. x64 on Windows 10 (entirely up to date 1/25/19) on a stand-alone desktop PC.]

I’ve run into a problem with this version of LOWriter that I don’t recall having before. I usually work with several documents open in Writer. Today, while trying to open another document, LO crashed. Well, fine. That’s not a problem. On recovery, however, I found that the specific file I wanted had reverted to a version after creating which I had manually backed up more than twenty (20) times. (I’m really conscientious about manual backups.) And the crash before this particular crash had done something similar but not quite as breathtaking as ignoring twenty manual backups.

I’ve never before had to go looking for manual backups. Could someone please tell me where they’re stored? And for the hell of it, where are the automatic backups kept? And the automatic copies? (Yes. I have Writer set up to make all those too.) Any ideas on why Writer may be ignoring all those backups and copies?

Thanks in advance for any helpful tips.

Later:

I found the backup copy as indicated in the Tools/Options/LibreOffice/Paths listing. I went and opened the backup there indicated. And the backup copy was the same as the copy recovered after the last crash. In other words, the recovery process worked fine. The backup process seems to be the problem. At all previous crash times I’ve successfully and automatically been restored to the documents I was working on as they were when LO crashed. Is there something new that would prevent this? Is there something now that would make automatic backups (which I have set to 20 minutes) superior in some way to manual backups so as always to revert to the automatic backup and ignore the manual backups?