Mac Sidebar Favorites keep disappearing

I keep a number of folders in the Favorites list in the sidebar of Finder windows—or at least I try to. Over the last few months, my Favorites keep disappearing. They will be there one day, and then the next day I find that with Favorites displayed in Finder windows, the only Favorites listed are the default ones: the hard drive, my user folder, and Recents. All the other folders I've added to Favorites are gone. This has now happened several times: I add them back, and within a few weeks they disappear again. (2020 iMac, Ventura 13.4.) Any suggestions?